Special Skills Rank

Note: The rank was made with three things in mind: How it can make difference in uncommon battles? This support/attack move can really change battle course? This damage can OTK? Except the E and F Rank ones, all the special skills are good, so anyway, you can use them! If the special skill is in D Rank, for example, it doesn't mean you need avoid use them!

Other observation, literally, almost all specials can OTK enemies (according by this ML Fandom Page)

OP Tier

 * Electrex - Thunder Twister (AoE 90 Thunder dmg)
 * Flickie - Meteor Strike (AoE 70 Fire dmg + Burn + Daze)
 * Giragast - Wizard Fireworks (AoE 80 Magic dmg + Blind)
 * Metanephrops - World Water War (AoE 60 Water dmg + Freeze)
 * Sealion - Mercury Wave (AoE 80 Fire dmg + Slow)

SS

 * Esmelter - Spin to Win (AoE 65 Metal dmg + Metal Weakness)
 * Heimdal - Epic Blitzgreig (AoE 65 Metal dmg + Daze)
 * Jonskeer - Spikefield (AoE 65 Metal dmg)
 * Lesaki - Thunder Storm (AoE 65 Thunder dmg + Metal Weakness)
 * Manolyth - Help me, Master (AoE 65 Magic dmg)
 * Omethyst - Massive Crystalization (AoE 60 Metal dmg + Metal Weakness)

S Tier

 * Dolphchamp - Ten-Tackles (150 Magic dmg)
 * Firanda - Panda Wrath (170 Fire dmg + Daze)
 * Gigram / Terror Dactyl - Thunfire (120 Thunder dmg + Burn + Moderate AoE Damage)

A Tier

 * Bloomskips / Greenasaur - Forest Wind (Team NER + Heal)
 * Sheluke - Lust Regrowth (Team NER + Heal)
 * Utochomp - Devour (AoE 50% chance to instant kill)

B Tier

 * Shock Turtle - Tension Drop (Half Life [Reduces 50% of total life for 3 turns])
 * Succuba - Manipulate (Mega Possession)

C Tier

 * Firekong - Burning Stick (80 Fire dmg + Burn)
 * Flawless - Mirror Mirror (Team Skill Mirror)
 * Pyrook - Kamikaze (100 Magic dmg + Self Instant Kill)
 * Vixsun - Heal Wind (Team 10% Heal for 10 Turns [Healing Wind])

D Tier

 * Gastosquish - Healthy Minerals (Team 40% Shield + Regeneration)
 * Obsidia - Strength of Ages (Self Double Life + Taunt)
 * Rockneto - Magnetic Force Field (Team 40% Shield)
 * Rarawr - Totem of Protection (Self 100% Shield + Taunt)

E Tier

 * Blesstle / Light Sphinx / Pelitwirl - Light Surge (50% Stamina Drain + Self 100% Stamina Restore)
 * Raydex - Back in Time (AoE Back in Time [The monster turns into his juvenile form and gets -40% damage])