Cyborg Freeza: 160,000,000
King Cold: 120,000,000
Thanks to his cybernetics, Freeza know has the greatest power in the universe, possibly enough to defeat Goku on his own. His father, described as "somewhat" below him in the Daizenshuu 7, makes it a walk in the park.
Worth noting these are the hypothetical Full Powers, what the Z Fighters were sensing where much smaller Kis since they were in a relaxed state.
SSJ Trunks: 157,500,000
SSJ Goku: 150,000,000
SSJ Vegeta: 152,500,000
SSJ Gohan: 155,000,000
Trunks is stated to have the same Ki as Goku and be around the same as Gohan, and Piccolo isn't even sure if Vegeta surpassed Goku. Tenshinhan lumps all the SSJs together as well, as do many statements that make the SSJ power seem like a very closed tier. Vegeta implies he's surpassed Goku based simply on birthright, so this should apply to the other Super Saiyans as well.
The real difference lies in fighting ability. Goku and Vegeta are portrayed to be fighting geniuses, often holding their own against stronger enemies and always looking to become stronger. On the other hand, Trunks and Gohan's blood makes them too human, not taking as much pleasure in fighting and not even knowing it was possible to surpass the Super Saiyan.
Piccolo: 2,250,000
~ Merged with Kami: 225,000,000
Gohan: 3,000,000
Training with a Super Saiyan is always good, but bodies have limits. Gohan ought to max out around the same level of other Base Saiyans, and genetics would determine Piccolo is below even that. But Piccolo is the most experienced fighter of the two, and a safer bet to face the Androids than the inexperienced Gohan.
After merging with Kami however, the tides turn. Piccolo far surpasses the Super Saiyan, to a point where his power up knocks Vegeta out of the form. He can also rival both the Androids, as per #16's words.
Kuririn: 30,000
Tenshinhan: 7,500
Yamcha: 5,000
Chaozu: 1,500
I thought about lumping them together with Piccolo and Gohan, but I'd like to make an analysis of the humans here. We have a upper ceiling for them: The narrator says a human body would be crushed by 100G as Goku trains on it, and by Jeice's reaction even 60k is beyond "Saiyan limits", let alone human ones. Kuririn also says he can never catch up to Ginyu Force levels and Nail, a Namekian Warrior, arguably had his Power unlocked by Guru as well, so humans should be a good amount below 40k.
For anyone other than Kuririn it's even worse, as their inability to master Kaio's techniques would imply they couldn't master their Ki as good as Goku, let alone become as strong. Tenshinhan gets the closest with his OP Shin Kikoho, but Yamcha and Chaozu aren't implied to have done anything like that.
Android #20: 1,800,000
Android #19: 500,000
~ Post absorptions: 1,500,000
Fodder.
Android #18: 200,000,000
~ Future: 120,000,000
Android #17: 225,000,000
~ Future: 135,000,000
These are the guys Trunks was talking about, and they're even stronger in this timeline for... Whatever reason. Vegeta can still keep up with #18 thanks to his outstanding fighting senses, but his punches lack the weight to do any damage and his stamina isn't infinite. #17 is a bit stronger than #18, and a dead even match with Kamiccolo.
As for the Future Androids. They are superior to the Super Saiyans in numbers, stamina, fighting ability (Trunks and Gohan were pedestrian fighters) and cannot be sensed at all. The one thing that should guarantee Gohan and Trunks' confidence and survival is superior power, although you could argue the twins held back to keep them alive, that's never implied. #17 or #18 even seems surprised to see Gohan and Trunks again, so it sounds more like they didn't care whether the guys survived or not.
Android #16: 375,000,000
Cell (1st form): 165,000,000
~ 1st form (Post absorptions): 375,000,000
~ 2nd form: 600,000,000
~ 2nd form (Full Power): 750,000,000
#16 is Gero's strongest creation... Behind Cell. But Cell has to work his way to the top: Somehow having lost his original power, he's below even the Androids and sees Vegeta as a threat, even though Vegeta shat bricks to his power. With the absorption of hundreds of thousands of humans he's a even match to #16, and absorbing #17 makes him capable of casually tanking a punch to the face from #16. And he's not even at Full Power.
By the way, I'd just like to say Imp. Cell + #17 fits like a glove here for Cell's power. You guys should try it.
SSJ Vegeta (Post Rosat): 600,000,000
~ Powered up: 1,000,000,000
Thanks to his training in the Room of Spirit and Time, Vegeta is now capable of drawing enough power to far surpass the Super Saiyan. But it seems like he couldn't tame his body to handle such Ki, resulting in the buffing of his body.
SSJ Trunks (Post Rosat): 625,000,000
~ Power up 1: 925,000,000
~ Power up 2: 1,400,000,000
~ Full Power: 1,800,000,000
Same thing as Vegeta. Stated by Kuririn to be superior to Vegeta, what is true thanks to his higher potential, but he held back for his father's pride. After Vegeta's gone he shows enough power to spar with Cell and at full power can even beat him. If he where fast enough, that is. Here Trunks learns the reason Vegeta didn't do the same thing to fight Cell: This many muscles kills your speed.
Cell (Complete): 950,000,000
~ Serious: 1,500,000,000
~ Powered up: 3,600,000,000
~ Full Power: 7,500,000,000
~ Zenkai: 13,500,000,000
After absorbing #18, #16 points out Cell's still weaker than Vegeta on everything. What they didn't know was that this power was only the tip of the Iceberg, and a slightly serious Cell could tank Super Vegeta's blows. Another power-up and he's a couple steps above SSJ, but not even his full power can do anything to Gohan. Even after coming back with a huge Zenkai Gohan can keep him at bay with under half his power.
SSJ Goku (Post Rosat): 3,000,000,000
SSJ Gohan (Post Rosat): 3,600,000,000
~ SSJ2: 27,000,000,000
With their training in the Rosat, Goku and Gohan not only tapped into power above the SSJ Wall, but perfected it and went even further. This is the true SSJ1 power, as Goku puts out that's as far as they go. Without mutating into new transformations, that is.
Cell Jrs: 2,000,000,000
SSJ Vegeta (Post Rosat 2): 2,000,000,000
SSJ Trunks (Post Rosat 2): 2,000,000,000
Piccolo (Post Rosat): 300,000,000
All of these guys are reckoned to be far below Goku. Vegeta is confident on beating Cell this time and Trunks shouldn't be behind him, but he still puts more faith in Goku because he always manages to work it out at the end of the day. Both Saiyans seem to have taken Goku's route for powering up without stressing the body as well, as shown by their lesser muscular mass.
And... there's Piccolo. He trained.
SSJ Goten: 3,600,000,000
SSJ Trunks: 3,750,000,000
The new generation seems to be rather promising. At a young age Goten already has power comparable to a Grade 4 Super Saiyan in spite of not even knowing how to fly, and Trunks is a bit above that. Their half blood status makes them stronger than the pure bloods, but they still pale in terms of fighting prowess. You can see this when Trunks kinda overwhelms Vegeta as they spar, but Vegeta is quick to get the upperhand and punch him into submission.
Kibito: 3,000,000
Kaioshin: 1,800,000,000
~ Merged: 13,500,000,000
Kibito is a tough opponent for Gohan and cannot be beaten without Gohan resorting to SSJ. Piccolo acknowledges he's dimensions above Kaioshin and the later even manages to paralyze SSJ2 Gohan, but he admits being no match for SSJ Goku.
Pocus: 150,000
Yakon: 3,000,000
Dabra: 13,500,000,000
Babidi's goons. Pocus gets wrecked by Vegeta, Yakon can tango with Base Goku. Only real threat here was Dabra: Comparable to Cell in terms of raw power, and even stronger thanks to his magic. He's fodder to Goku and Vegeta when they go SSJ2, though.
SSJ2 Gohan (Post 7 years): 18,000,000,000
What a jobber. The story and Daizenshuu 2 seem to imply his power didn't change, aside from his SSJ2 self. His body still has the same amount of Ki, but he struggles to channel it into power properly now. Gohan never really trained as a SSJ2 and still had to rely on his emotions to transform, but since acknowledges being incapable of drawing power from anger now he can't tap into all of his power anymore.
SSJ Vegeta (Post 7 years): 3,200,000,000
~ SSJ2: 24,000,000,000
~ Dormant Power Unlocked: 30,000,000,000
Confident he can beat Goku until he senses SSJ2 Goku's power, to which he lets Babidi take his soul so he can be stronger. Without Babidi's influence, the dark power seems to be gone.
SSJ2 Goku: 30,000,000,000
~ SSJ3: 150,000,000,000
Goku was seemingly uncapable of growing stronger in his Base or SSJ selves as he told Gohan 7 years prior, so his power ups derivate from the new forms he achieved. He perfected SSJ2 and was capable of surpassing even Gohan, and SSJ3 is even further above that, being the pinnacle of Super Saiyan power. But SSJ3 seems a dangerous form: It eats away not just Goku's Ki but his life energy, forcing Goku to return to Heaven much earlier than expected. Guess that's what happens when you draw out all of your power with such a unstable form.
Majin Boo: 22,500,000,000
~ Powered up: 135,000,000,000
~ Good: 60,000,000,000
~ Evil: 75,000,000,000
~ Evil (Good absorbed): 1,000,000,000,000
~ Evil (Gotenks absorbed): 2,250,000,000,000
~ Evil (Gohan absorbed): 2,500,000,000,000
~ South Kaioshin absorbed: 1,500,000,000,000
~ Pure: 150,000,000,000
Majin Boo starts as fodder that's laughed away by Vegeta, but he constantly power ups into a nigh invencible opponent. The original Majin Boo caps out on SSJ3 Goku's level, but he ends up expelling his evil self for the cost of over half his power. The Pure Evil Boo beats the Good one and eats him; returning to the original Majin Boo but without Dai Kaioshin's influences blocking his power. He gets beaten by Gotenks and Gohan but absorbs them. After Majin Boo is stripped of all his absorptions, he returns to his original, feral self that's a fairly even match to Goku.
Gotenks: 90,000,000,000
~ SSJ: 180,000,000,000
~ Post Rosat (Base): 250,000,000,000
~ SSJ: 1,250,000,000,000
In Goku's eyes, two gifted squirts merging results in a guy powerful enough to beat Majin Boo. Piccolo seconds this with his own eyes. But a powered up Majin Boo is beyond the expected, and Gotenks is sent to the Rosat. Piccolo thinks Gotenks can win without even transforming, but ultimately the boys need SSJ3 to get the upperhand.
And I know, the multipliers are wrong. But who cares? Gotenks is massively stronger than Goku either way, be it 10x or 1,000x times. I just didn't want to make this list a endless string of zeroes.
Gohan (Dormant Power Unlocked): 1,500,000,000,000
The strongest unfused character in Dragon Ball Z. That's the ultimate peak. It's always been hyped that Gohan has the biggest potential (Other than perhaps Goten and Trunks) thanks to his hybrid blood, and Old Kaioshin's ritual pushed him further than even his natural limits. He far outstrips his father and even Majin Boo, but that doesn't make his fighting abilities any better, and he still loses to Majin Boo
Super Vegetto: 6,000,000,000,000
Goku/Gohan Potara merge: 2,700,000,000,000
SSJ3 Gogeta: 1,500,000,000,000
A Goku and Vegeta fusion, that's definitely the strongest. At least that's what Old Kaioshin and the El Manga Legendario said. Goku and Vegeta's rivalry pushes their fusions to be even stronger than a fusion between Goku and Gohan, the strongest unfused characters. That same Goku/Gohan fusion was stated by Old Kaioshin to be capable of takin on Gotenks-Boo without transforming, so I take it that Vegetto transformed just to be safe.
As on Gogeta, he's naturally weaker than Vegetto in all regards, and weaker than even Gohan-Boo going by both Boo himself and Goku, but at least he can still beat normal Super Boo. I had my doubts on whether he could become a SSJ3 or not since Vegeta isn't one, but I guess Gotenks' own inability was caused by Goten and Trunks probably having not perfected the SSJ form yet.