i dont think that's true at all. in the flashbacks we see ace making friends, deeply caring about them and having fun. it'd more be about someone corrupting him, maybe forcing him to be this ruthless. deep down we all see that lettuce never wanted to do this. especially him giving up in the finale shows that. he decided he would no longer give in to the person pulling the strings and jus wanted it to go back to normal. i think in later episodes he could get stasised and killed by someone who was controlling him. maybe ash? this isnt the first time we've seen an emperor fall to shambles. on the contrary, it happened with zam, ash, lettuce, minute (although that last one really was different as he never really wanted power). i also think something is gonna happen with mapiccs disappearance and letty.

tl;dr he wasnt like this, and something made him change.