What did Estarossa do to the revenge counter of Meliodas in the Episode 20 Season 2 of Nanatsu no Taizai?
It's all about Estarossa's commandment. I read some site about it that his commandment can suppress Meliodas's Revenge Counter.

Estarossa's COMMANDMENT


  "Those who stand against him with hatred in their hearts will be
  rendered powerless, and will lose the ability or capacity to inflict
  harm or damage to any persons in his presence." This allows Estarossa
  to negate any type of power or attack that bears animosity, and was
  potent enough to completely nullify Meliodas' Revenge Counter


link:https://comicvine.gamespot.com/estarossa/4005-133352/