Glalie

Glalie is unlike any other Pokemon in the Battle Spot Singles metagame. Its viability solely stems from its ability Moody. Once Glalie is given a free turn or is able to outspeed the foe, it can spam Substitute and Protect until its appropriate defenses, Speed, or evasion sharply rises.

However, Glalie's overall frailty, weaknesses to common attackers such as Mega Charizard X, Mega Charizard Y, and Mega Metagross, and lack of relevant resistances mean that it cannot be expected to see meaningful long-term success if simply tossed onto a team. Glalie is almost exclusively used to improve a dreadful matchup against defensive teams or paired with a paralysis user such as Thunder Wave Mimikyu, Thunder Wave Cresselia, or Glare Serperior that allows it to repeatedly use Substitute against a paralyzed foe until it gets fully paralyzed. Even when Glalie gets a free turn, it can be checked by opposing Ice-types, Taunt, status moves, phazing moves, attacks that go through Substitute like Hyper Voice, and attacks that ignore evasion like Sacred Sword. Despite all these weaknesses, once Glalie is allowed a free turn to use Substitute, it will likely gain the correct boosts and eventually steamroll an unprepared foe.