There's no "not easily" in threads like these. It doesn't make sense. Either one character's matter/reality/time/universe manip. works better, or the other does. The comparative power of the two may be close, but whoever wins, the fights would be over in moments. Like, if the IG trumps AM's control over reality, is Thanos really going to have to struggle mightily for minutes/hours to erase him from existence? Sometimes in comics we see a bit more of a struggle for dramatic affect, but given how the powers work, someone would be erased quickly and it would be done.
