Hunter x Hunter: Neteru vs. The King
Vinland Saga: Thorkkell vs. Thorfinn
Bleach: Ichigo vs. Aizen
Dragon Ball: Goku, Vegeta, Mr. Satan, and Buu vs. Kid Buu
Hajime no Ippo: Takamura vs. Hawk
Either way, Vinland Saga: Thorkkell vs. Thorfinn get's my vote.
Let me just say that Hunter x Hunter: Neteru vs. The King and Hajime no Ippo: Takamura vs. Hawk were also pretty good. And i don't need to say nothing about the DBZ's right ?
I nominate :
Sasha VS The Tanners Brothers (Qwaser of Stigmata)
Chikane vs Homura and the Masked Woman (Zettai Shoujo Senki Amnesian)
Tori and P-01s VS Seiren (Horizon on the Middle of Nowhere)
There's also others but I am lazy to list them (for the moment).