through thick thin (adverb) firmly: with determination
Sinonime: adamantly,
constantly, decisively, doggedly, indefatigably,
intently, obdurately, obstinately, perseveringly, persistently, pertinaciously, purposefully, resolutely, staunchly, steadfastly, stolidly, strictly, stubbornly, tenaciously, through thick and thin, unchangeably, unwaveringly, with heavy hand
Antonime: changeably,
indefinitely, waveringly, weakly