This is a simple mod that will detect players with more than 120 skill points and mark them as a cheater using Overkill's built-in system. It's sad that this obvious cheat isn't already checked by that system.

This is very useful as both host and client, though if you're host, I recommend the extremely great mod Lobby Settings, which can kick skill point cheaters when they're connecting to you, among other incredibly useful things like setting an Infamous Limit and saving your default lobby settings.
And also, the thumbnail was made with Lobby Player Info. Both of these mods are absolutely essential and way better than mine :)