Magma Pummeler

The counters aren't a size, they're ammunition. Most X-cost creatures that arrive with +1/+1 counters spend them on the battlefield as raw stats, hoping to connect in combat; here the counters are a store of burn waiting for a trigger. Any damage dealt to it while a counter remains is prevented and replaced by peeling counters off, and each removed counter redirects that much to any target, which turns every block and every burn spell aimed at it into reach pointed wherever you want. The design inverts the usual relationship between defense and offense: an opponent's attempt to fight through it is the very thing that fires the payload, and because the damage is prevented rather than absorbed, the body survives to do it again as long as counters remain. The shield only answers damage, though, which leaves a clean exploit: any destroy, exile, bounce, or -X/-X effect walks straight past the counters and removes the creature without ever setting off the redirect. Combat and burn are the traps; removal that never deals damage is the honest answer. The timing rewards a careful read: the damage is prevented and the counters come off first, and only then does the redirect go on the stack, so a single large block converts a chunk of the creature's size into reach that ignores blockers entirely. You raise the counter total not for the swing but for the threat of what happens when someone swings back.