Poison Heal Breloom is one of the best Tentacruel counters as it benefits from Poison and is immune to Scald burns, whilst it can use Tentacruel as setup fodder.
Would you mind rewording this to make note of how it can't directly switch-in to Tentacruel without already activating its ability? This was bugging me, especially since it's listed at the top of the checks & counters list..