How to fix out of level foundation walls
Concrete that's &quot;fixed&quot; like this is sure to begin crumbling right after the contractor moves out of state. I'd be dissatisfied with this. As far as I'm concerned this is a breach of contract and is the contractor's responsibility, even as far as removing the entire thing and doing it over. That's out of scope for this site, though.
The only fix I'd DIY is to level the top wall plates and cut the studs custom to fit below. You'll then have to deal with the situation when you install siding, etc., so it is all parallel with the top plate. I would not fiddle with concrete repairs that may not hold up well.
One possible fix by others that I might deem satisfactory would be to have a skilled mason lay a shorty block row on the footings, level on top, and built up with mortar below where needed. That could be poured full of concrete to retain the integrity of the current foundation.