To ask (hopefully) more specifically the question others have asked: is it what happens on the last page that feels unsatisfying, or do you feel like the prose isn't up to snuff? Option B is cosmetic and can be fixed in post, so to speak, but Option A might be a much bigger problem.
It also depends how important the events of the last page are, and what they may point to. If you're just tying up loose ends, why is it that some particular loose end won't tie up the way you want, or just doesn't feel right even though you tied it up? Maybe if you follow the thread you'll find a structural problem--the actual events of the climax and ending aren't satisfying, which is why you can't achieve that sense of closure that a last page needs. In that case, fix before querying.
On the other hand if you just think you should have a last sentence/paragraph that sounds cooler, you'll probably come up with that eventually, and an editor won't think it's a big deal.