How much revision is too much revision? (writing)

That's where track changes come in handy. I make a correction, do a quick qualification or comment on each change, and let the other person decide. Because I am fairly decent, but not perfect, in my language abilities. If there are so many changes until the entire page turns red (e.g. because the other party has terrible grammar), I won't show the other person the editted version, but ask the other person to PROPERLY check for grammar before sending me again.

tl;dr they sent me so they're asking me for help. They can make a choice but they better be prepared... I warn them beforehand too.

Hadriel