Antonyms of adj relentless

2 senses of relentless

Sense 1
grim, inexorable, relentless, stern, unappeasable, unforgiving, unrelenting -- (not to be placated or appeased or moved by entreaty; "grim determination"; "grim necessity"; "Russia's final hour, it seemed, approached with inexorable certainty"; "relentless persecution"; "the stern demands of parenthood")

INDIRECT (VIA implacable) -> placable -- (easily calmed or pacified)

Sense 2
persistent, relentless, unrelenting -- (never-ceasing; "the relentless beat of the drums")

INDIRECT (VIA continual) -> sporadic -- (recurring in scattered and irregular or unpredictable instances; "a city subjected to sporadic bombing raids")

Similarity of adj relentless

2 senses of relentless

Sense 1
grim, inexorable, relentless, stern, unappeasable, unforgiving, unrelenting -- (not to be placated or appeased or moved by entreaty; "grim determination"; "grim necessity"; "Russia's final hour, it seemed, approached with inexorable certainty"; "relentless persecution"; "the stern demands of parenthood")
       => implacable (vs. placable) -- (incapable of being placated; "an implacable enemy")

Sense 2
persistent, relentless, unrelenting -- (never-ceasing; "the relentless beat of the drums")
       => continual (vs. sporadic) -- (occurring without interruption; chiefly restricted to what recurs regularly or frequently in a prolonged and closely spaced series; "the continual banging of the shutters")