Nishiki's transformation from best friend to main villain is handled really well, one of the most gut wrenching character arcs I've seen.
1
Yakuza 3
Yoshitaka Mine
Has such a presence in every scene he's in, and when his motivations are revealed they make complete sense (although that reveal is a little rushed).
2
Yakuza 0
Daisaku Kuze
One of the most memorable villains in the series. Very cool and intimidating; and I love seeing how his dynamic with Kiryu changes between each of their encounters.
3
Yakuza 0
Keiji Shibusawa
A final boss reveal done right.
4
Yakuza 5
Masato Aizawa
I understand what they were going for here, but Aizawa's role as the final boss is extremely underdeveloped. While his motivations are very interesting, he feels like a different character than the one we saw in earlier scenes.
5
Yakuza Kiwami 2
Ryuji Goda
Don't really get the hype for this guy. He's fine, but I never found his personality or dynamic with Kiryu nearly as compelling as villains that have come before and after.
6
Yakuza 4
Hiroaki Arai
I still don't know what he wants.
7
Yakuza 4
Isao Katsuragi
He's just really evil, and despite being portrayed as intelligent he makes some pretty dumb decisions.
8
Yakuza 4
Seishiro Munakata
He's just an asshole.
9
Yakuza Kiwami
Kyohei Jingu
He's just an asshole.
10
Yakuza 5
Tsubasa Kurosawa
One of the most disappointing antagonists I've ever seen. He has a very interesting presence in the story until he's revealed to be a mustache twirling villain with an idiotic master plan.