Just like the title says, Thor goes against each of the 13 captains of the Soul Society, 1v1 (*one fight exception is 2v1) :
Ichimaru
kurotsucki
Kaname
Soi Fong
Komamura
Aizen
Toshiro
Kenpachi
Uhitake & Kyouraku (*the exception, as they're portrayed as twin swords/warriors, intended to fight together in lore).
ByaKuya
Genryusai
**Unohana Retsu not fighting cause well, she doesn't fight, she heals. Ok, so I guess 12 captains./shrug**