Vengeant Paladin

When Vengeant Paladin enters the battlefield, it gains indestructible until end of turn. Choose a creature. Vengeant Paladin fights that creature.
Vengeant Paladin can't block any creature other than the chosen creature. Whenever Vengeant Paladin blocks or becomes blocked by the chosen creature, Vengeant Paladin gets +X/+0, where X is that creature's toughness.