Kingdra

It stores energy by sleeping at underwater depths at which no other life forms can survive.

Ability — Deep Sea King: When your Active Pokémon is Knocked Out by damage from an attack from your opponent's Pokémon, you may move any amount of Water Energy from that Pokémon to this Pokémon.

Aqua Burst (40×): This attack does 40 damage for each Water Energy attached to this Pokémon.