死磕

死磕	sǐ kē	(coll.) to fight to the death
死	sǐ	to die / impassable / uncrossable / inflexible / rigid / extremely / damned
磕	kē	to tap; to knock (against sth hard); (esp.) to knock (mud from boots, ash from a pipe etc) / (fandom slang) to be into (a character relationship, dynamic, or trope)
磕	kè	variant of 嗑