Who is stronger a pitbull or rottwieler?

Depends what strength you are seeking. A pitbull is wild with endless energy and heart. A rottweiler is focused and much stronger when it comes to bite force, but tires quickly. A very game pitbull will do better pulling heavy weights in competition than a rotti. This is all pending the properly bred pitbull and the properly bred rotti. You are also comparing a pitbull (technically no standards since it is not recognized by any official groups) to a rotti (recognized by official groups with real solid standards).