Twinblade Paladin

Whenever you gain life, put a +1/+1 counter on this creature. As long as you have 25 or more life, this creature has double strike. (It deals both first-strike and regular combat damage.)

From Magic: The Gathering.

Open the interactive version on https://mythscribe.cloud/app/tcg/cards/cms6o60cr3d07pb1hdxymzpwe.