Relentless
[Body Heat (April 1, 1981)]
Indicates unceasing activity, generally irritating to the speaker. Less commonly used as a term of admiration or respect. The victim of Body Heat upon realizing how screwed he was: “Don’t you understand? She was relentless!” “It’s so relentless!” used for relentless inanimate objects.
February 1983. Kissing the Pink Naked “Big Man Restless” – “He’s so relentless”
– Neal Manson (1985)