Tirelessly
Part of speech: adverb
Definition: In a tireless manner; without tiring, flagging, or ceasing.
Example sentence: I work tirelessly advocating for gun violence prevention and promoting common-sense gun laws that could spare other parents the pain of having their child taken by senseless gun violence - laws the NRA's leadership has fought against relentlessly.
Indefatigably
Part of speech: adverb
Definition: In an extremely persistent and untiring manner; in an indefatigable manner