It’s perfectly grammatical. Personally, I’ve always abhorred that comma there: I can see no reason whatsoever for it to be there, I find it distracts and confuses far more than it helps … but alas, I am not yet supreme timelord ruler of the known and unknown universes, so I can’t really dictate how other people feel about it. Yet. But if you wish to be on my good side once I do become supreme timelord ruler, etc., then leave out the comma and just write, “Making that which needs to be better”. (Or, alternatively, “Improving what needs improving”, for that matter.) —
Janus Bahs Jacquet Jan 10 at 10:59