Remember when Gamzee was one of the most powerful trolls? Im not talking classpect wise, I mean physical strength. Out of the 12 beta trolls, he was the most powerful, the fact that he could control it adds to it, as he doesn't break everything he touches (unlike Equius). In Caliborns session, he couldn't be killed, not because he was a godtier, as that was just a costume, but because of "Evil Clown Power". I think that the reason as to why he died in Beyond canon, is due to the fact that he was trying to redeem himself, and in that he had removed his "Evil Clown Power". Another reason for his death in Beyond canon is the fact that he wasn't necessary to the plot anymore, as sburb needed him to live to create the time loop with Caliborn/Lord English.