Tatsumi (Akame ga Kiru!) vs. Guts

Both characters are swordsmen and have cut down big beasts.

Scenario 1: Tatsumi fights Golden Age Guts.

Scenario 2: Tatsumi fights Black Swordsman Guts.

Scenario 3: Tatsumi gets Incursio and Guts gets the Berserker Armor.

The only fight Guts might win is 2. Tatsumi's first scene (when he was a weak noob) had him killing a huge dragon in a single slash.

Incursio Tatsumi is complete overkill for any version of Guts.