suru verb (special), intransitive verb
degenerate; lapse into; fall into
Literary and somewhat formal. Often used with nouns indicating a negative state, such as 堕落, 悪習, or 怠惰. The construction is typically ~に堕する.
彼は安逸な生活に堕してしまった。
He lapsed into a life of ease and comfort.
一度悪
Once you fall into evil ways, it is hard to get out.