I'm rewatching Cooler's Revenge and I think that Cooler's got a really interesting character.
He's like a foil to Frieza but at the same time he's different. Cooler doesn't let his emotions/rage show while Frieza outwardly blows up/lets his temper get the best of him. Other than him being different to Frieza, another neat thing about Cooler is that he does things out of resentment and hides his true thoughts. He went to earth to try and kill Goku and he acts like it's to avenge his family's reputation- not to avenge his brother.. and yet it actually seems the opposite given the way he talks and acts about it.
("I never did like him, and now he goes and disgraces my father and I by being killed by a saiyan." ¹, "I don't know who this saiyan thinks he is but noone attacks our family and lives. NO ONE.."², Cooler blowing up at his squadron over them failing to kill Goku and Gohan³, the fact that he chose to try and kill Goku first instead of going straight to blowing up Earth because it's more personal..)
Outside of his emotions not showing, he shows respect towards other beings that aren't him and sometimes steps in to help (his squadron and Xeno Trunks in SDBH) when Frieza or King Cold don't tend to do that. Despite being evil he seems to care about certain individuals to some aspect. Cooler literally STEPPED IN when Salza was in danger and if you've read Super Dragon Ball Heroes he teams up with Xeno Trunks at one point despite having no motive or 'in' for doing so.Even extra/non-canon material like Xenoverse 2 has him talk highly of his squadron and there's dialogue where he says something along the lines of them making him soft- a huge contrast to how he's described as more brutal and violence-inclined than even Frieza.
I feel like Cooler seems cold and collected, but he's actually not and he's more emotional (and ruthless lol). If he ever becomes canon I hope they still keep this aspect of him since it's rarely talked about. For a cold-blooded lizard he has a surprisingly warm personality. If anyone has thoughts I'd be glad to hear them, thank you.
(Cooler is Dragon Ball's underrated kuudere.)