Mistcutter Hydra can't be countered. Haste, protection from blue Mistcutter Hydra enters the battlefield with X +1/+1 counters on it.
Official Rulings for Mistcutter Hydra
9/15/2013 : Spells that can’t be countered can still be chosen as the target of spells or abilities that try to counter them. Although the spell won’t be countered, the spell or ability that tries to counter it will resolve, and any other effects of that spell or ability will happen.