Technically this is probably very difficult to pull off in a real match. In the case that a users Max Health manages to go under 0 max health, they will become immortal. this was found via me and my friends messing with the siphon bullets upgrade, constantly killing the testing abrams until they became immortal. This was since reproduced consistently on real players in the testing lobby. While this would be incredibly impossible to do in a real match, this should probably be fixed before someone finds out a way to use it.