godan verb (-su), transitive verb
Used for personal retaliation or getting back at someone for a wrong. Often implies a direct, sometimes petty, payback.
いじめられた友達のために、彼は仕返すつもりだ。
He intends to take revenge for his bullied friend.
あんなことをさ
If someone did that to you, you'd want to get back at them.
godan verb (-su), transitive verb
do over again; redo; start over
Used when repeating an action from the beginning, often because the first attempt was unsatisfactory. Less common than やり直す.
計算を間違えたので、最初から仕返した。
I made a mistake in the calculation, so I redid it from the beginning.