At least "do the needful" is somewhat correct and parseable. It was even used in Victorian England.[1] Anyone can understand it means "do what's necessary". It's old and weird, but not wrong.
"revert" and "reply" are entirely different words that sound kind of similar.
I’m not Indian but I love “do the needful”. I’ve only ever encountered it when people used it for humorous affect. Something about it makes me smile.
It's much less amusing when it's used seriously by a lead engineer who clearly hasn't actually thought about what "the needful" is and who clearly just wants to pass off the "ask" you "brought them" to someone who clearly doesn't know what "the needful" is.
I was replying to an email about an interview, and beginning "Please do" (not consider me for this job any further), and my (Android) phone autocompleted "the needful".
Rather interesting considering I don't think I had ever typed it.