Maybe you could use a block filler.
I know you said it's concrete, but block filler goes on fairly easy and expands slightly to fill the imperfections in blocks.
Maybe, it will work for you in this situation.
Other than that, the only way I know of to get a perfect finish on a wall like that is to glue drywall right over the concrete. Do a test to see if there is a moisture problem first, duct tape a piece of plastic to the wall (it needs to be the size of a plate or bigger), then after a day or 4, or a week, peel it off and look for moisture or dampness, discoloration, etc. on the wall.
If no trace of moisture, your options are wide open.
Slight moisture, try a sealer like UGL.
If the plastic is wet, find the problem.
The reason I suspect moisture is the fact that this wall was worse than the rest. Try the test, it may affect your decision of what to do.