Jisho

Hello. I don't know for sure either, but after looking in some native sources for a little bit i found this:
「いてまう」は、ひどく痛めつけることを意味する関西の言葉。 「いってしまう」が元とされる。
""いてまう" is a Kansai word that means to hurt you badly. It is based on "いってしまう".

This too:
殴る、蹴る、投げる、極めるなどの攻撃を加えようとする事を意思表示する言葉です。
It is a word that expresses the intention to make an attack such as hitting, kicking, throwing, or mastering(?.

Others:
to fail; die; go bankrupt, attack viciously

You have to check if that even makes sense in the context of the manga that you are reading.
Hopefully i helped you.