looking for "wincon" activated abilities in grixis

so im making a [[mairsil, the pretender]] deck, when she etbs she can exile a creature/artifact from my graveyard/hand and put a counter on it, then she has the activated abilities of all cards with said counters on them.

primary caviat being she can only activate them once each per turn. otherwise any +2 mana ability with a -1mana untap would go infinite, and many more busted interactions.

the whole plan of the deck is to sort of get around that by flickering/copying mairsil, but for the most part I'm just capitilsing on a lot of once per turn actions or cheesy abilities of big creatures.

anyway, I need a way to close out the game, I had a few other deck ideas like going for modular where winning would be as simple as swinging,

but so far I'm finding it hard to balance the large array of draw & ramp cards with cards that just pump mairsil a bit.

TLDR/Conclusion
so really, I'm just looking for a (big) card I can exile with mairsil, and activate to get people out or close to out, so far the best I've come up with is [[heartless hidetsugu]], whilst it isn't really lethal, it puts the pressure on a lot and I can run a card like [[phyresis]] with it to make it lethal if they are over 20 health.

NOTE: there are quite a few creatures that can basically ping everyone for one for "free" or a low-cost, but just pinging for 1/2 a turn might not be ideal (unless they are like truly free, and then I can do it on each opponents turns and it adds up)