Boar

Charge. If the boar moves at least 20 feet straight toward a target and then hits it with a tusk attack on the same turn, the target takes an extra 3 (1d6) slashing damage. If the target is a creature, it must succeed on a DC 11 Strength saving throw or be knocked prone.

Relentless (Recharges after a Short or Long Rest). If the boar takes 7 damage or less that would reduce it to 0 hit points, it is reduced to 1 hit point instead.