Gluttonous Hellkite

The cast trigger is where the whole thing happens, and it fires before the Dragon ever reaches the battlefield: while the spell is still on the stack, each player sacrifices X creatures, and every one of those deaths (yours and theirs) feeds two +1/+1 counters onto the body that's about to land. That symmetry is the load-bearing tension. A pure edict that only clipped opponents would be a control tool; forcing yourself to feed the same X makes this a payoff for a board you were already planning to spend. The card wants a sacrifice engine underneath it so the X you pay yourself is a resource conversion rather than a loss, and it turns opposing go-wide boards into your own stat line. Because the counters are counted from the total sacrificed, a symmetrical X of, say, three across a full table can produce a flyer far larger than its mana would suggest, arriving already evasive with trample to push the trampled-over damage through. Note the timing floor: with no other creatures anywhere, casting it for X of zero yields a plain 3/3 with flying and trample, which sets the honest baseline the counters build up from. It reads as a finisher, but the mechanically interesting read is as a board-state converter that happens to leave a Dragon behind.