I remember beating a Chainsaw only run of Doom 2 GBA on the second difficulty. Back then, I had discovered an AI exploit with Cyberdemons in which, if you pin them against a wall or ledge they can't cross and chainsaw them, they'll keep taking damage while looking away until they die. This sometimes backfired (no pun intended), resulting in them turning around to launch rockets at my face, but I just kept at it until I succeeded. For Spider Masterminds, I usually let them infight as their hitbox felt wonky to hit with the chainsaw.
Too bad I couldn't saw the Romero head.