Hello everyone and welcome to my 133rd analysis, this time featuring Learnean.
In terms of movepools, Learnean has one of the most deadly ones due to the vast array of debuffs and 0 CD powerful single target attacks. His trait, Hardened, helps with all kinds of different effects, especially against Eggeater's Multi Effect Eggs, Frostwrath's effects and opposing Learnean in the Dragons book. However, aside from Speed, Learnean has a bad case of Base Stat problems, having less than ideal Base Life and outright bad Base Strength, the latter of which makes a terrible waste of powerful single target attacks, though this can be mitigated by ranking him up.

-Water Head Power
-Triple Chomp
-Confluent Power
-Blaze Head Power/Mixed Powers
Runes: 3 Speed/3 Team Speed/2 Strength 1 Speed/2 Speed 1 Strength

Water Head Power has a good Base Power, is unresisted, has 0 CD and drains 50% Stamina from the target-excellent to use against recently refreshed enemies. Triple Chomp also has great Base Power and 0 CD, is unresisted and Stuns the target. Confluent Power deals very minimal damage on hit, but it applies Stamina Leak, Poison and Burning to all enemies hit, which whittles enemies down in all aspects very fast. The last slot goes to either Blaze Head Power for another single target that Burns, or Mixed Powers to have a chance at refreshing all the Poisoning, Burning and Stamina Leak-plus, the Stamina Leak has a 100% chance of happening. 3 Speed maximizes his Speed and allows him to quickly use Confluent Power or Triple Chomp or whatever, but 3 Team Speed is also useful since he doesn't need stats to do damage. 2 Strength 1 Speed focuses on his powerful single target attacks to make him an attacker, but another approach here is 2 Speed 1 Strength, which outspeeds attackers.

Teammates: Along with AOE Poison and Burn, you can use either one of Ignite, Quicksand, Bleeding and Sunburn to wither down enemies alarmingly fast, although Learnean is still very good without specific allies.

Countering Learnean: Removing debuffs from your team will render Confluent Power useless. Make sure not to give him too many turns because his Water Head Power will start to hurt you later on in the game when you have to recharge, plus his 0 CD moves will start stacking up their damage if you don't have Healing or Shields.