Hancock had no mystery and no real charisma. Her whole point is the mera joke power.
Kuma had no personality but his fight with Zoro and then Sabaody incident were good. Also interesting powers
Doffy has character and his powers were cool too. Too bad his wankers make me dislike him a bit. And yes he was a YC4 at best in Dressrosa.
Moria was cool for me. Very nice powers but the story was his forte. Lost to Kaido and lose everything, even his will. I hoped for some kind of revenge sub arc for him in Wano but he got even more pain from BB this time.
Mihawk, his Baratie intro is probably the moment it make me love this manga. Too bad now it has fallen to this point.
Croco, pretty cool but nothing special for me. Your average mafia boss with sand powers. Also his free power jumps make him a big plot mistake, powerwise, for me.
Jinbe is meh. He is a fishman who uses water karate, his past with the sun pirates was not bad but never truly explored, but since they got destroyed by young Kizaru they must have been nothing special, far from yonko status. Also Jinbe joining / not joining for 3 arcs was tedious.