Activated ability to win the game?

trying to improve my [[mairsil, the pretender]] deck,

currently all of my ways to win the game require alot of mana & untaps, As well as a 2 card combo.

the mana & untaps are fine with me, but id like to try find a 1 card option.

Currently im winning the game by activating [[crypt rats]] for like 50 whilst giving it lifelink.

So ideally, im looking for a card thats a mix, aka alot of damage to everyone but me.

worst case scenario i run something like [[boommobile]] and activate it 3 times, but ideally its a one time activation for alot of damage.