fizzle out

verb

To lose excitement, to become less exciting; to end, fail or die out in a weak or disappointing way.
“Tottenham had hoped to make a statement of real intent against the title pace-setters and while manager Harry Redknapp did not secure the victory he craved, he at least saw his side match United every stride of the way in a game that fizzled out after a bristling start.”
“That would see the disputes fizzle out into an industrial relations zombie - neither living nor dead.”
To kill or end (someone or something).