Literally Infinite Lifegain/Pumpup/Game Winning Combo

This creature has echo , where X is your life total. (At the beginning of your upkeep, if this came under your control since the beginning of your last upkeep, sacrifice it unless you pay its echo cost.) When this creature enters, it deals an amount of damage of your choice to you and target creature. The damage can't be prevented.

Flying If noncombat damage would be dealt to you, prevent that damage. You gain life equal to the damage prevented this way. When Purity is put into a graveyard from anywhere, shuffle it into its owner's library.

Trample If damage would be dealt to another creature you control, prevent that damage. Put a +1/+1 counter on that creature for each 1 damage prevented this way. When Vigor is put into a graveyard from anywhere, shuffle it into its owner's library.