A very dark and calm motif, one of my favorites, fits Freeza very much for me
Here's some examples
Freeza's Hidden Power
Freeza's Army Arrives
Freeza & His Terrible Power
Merciless Freeza
Birth of Freeza's Army
Freeza Rules
Freeza's Scheme, Death Premonition
Freeza's Wish
An Unexpected Bounty
Freeza & Broly
Freeza's Ambition
But there's also Broly's theme, I think this one is more prominent than the Freeza motif (just wanted to talk about the Freeza one because I really like it
Broly's Theme (Title)
Broly The Wild Child
Broly's Rage & Sorrow
There are way more arrangements of his theme, it's basically the major motif in the movie.
Now, about Kikuchi, I really can't think about a theme that is more memorable than Piccolo's, most of the people just recognize Piccolo's Theme and the Instrumental Arregements of Makafushigi Adobencha, Cha La Head Cha La, We Gotta Power and We Were Angels when the point is Kikuchi score...
Maybe the Fourth Goku's Theme???
There's also Tapion's Theme, but this one just is more know because of his Ocarina arrangement, people doesn't give much attention to other tracks containing his motif.
Kid Gohan's theme is a pretty know one too, different of his Teen/Adult motif, which is unknow for most of the people.
But, if we go to the villains themes, Garlic Jr.'s Theme is no doubt the most well know one, it maybe can be just because of this track, but I think most of the people really know that this melody belongs to Garlic Jr.
Edit:
Also, important note: I'm just couting true character motifs, not insert songs or one single track that the "purpose" is to represent a character, like A Tyrant Revived, which a lot of people think is Freeza's theme, but that is definitely not true, at least not for me, it just sounds similar (most because of the choir), I just count a melody being related to a character when the melody appears in at least two tracks or more (As Bardock's theme in DBS Broly, the motif just shows up in two tracks), and this doesn't happen with any track in DBS Anime score (Except for the Chozetsu Dynamic and Limit Break x Survivor instrumental tracks, and Cha la head cha La as well).
I think a good proof that you can't relate one single track to a character, is the case of the track nammed "Jiren's Theme", which besides obviusly having the character's name on it, this track actually was never used for Jiren in the anime, this is the work of Sumitomo, the anime ost having a lot of random themes, and just the Movies ost having true character motifs, and this is a shame for me, I'm not a fan of the ideia of not including any motif in the Anime scores, Kikuchi included character motifs in both his anime and movies scores, I hope Sumitomo includes at least one or more character motifs when a new Super animes releases.
