How do i remove glue from walls ...read on please!?

We have this glue/adhesive something of that sort on our walls. A few years ago, I put some design applique on part of a wall. It is now ripped off and we cannot find anything. Tried DIF, Chomp, S.O.S. scrubbers, acetone even sandpaper. I also tried to paint over it (the walls will still be the same color). Google did not help. I hope someone can, please.