Sorry, but that screenshot proofs nothing. You can't see with what he hit you (could both be fists), how many hp you lost or even if it was intentional because he killed an enemy shortly after your report. Are you sure that the hit with the weapon wasn't just an accident during a fight? Don't get me wrong, if he really teamattacked you he should get a punishment but I think this is not enough for a ban request. If somebody punchs you just tell him to stop instead of reporting.
Admins already have enough work to do.
