Congress can of course pass laws concerning situations like the one in question, they can impeach and remove an offending official, cut a budget as punishment, etc. They can also authorize themselves to appoint a special prosecutor and then turn one loose on offenders. What’s lacking is will, not ability.
If I understand correctly, a DOJ investigation and prosecution does not use info fom a Congressional hearing.
But they lack the will? Clinton will never be held responsible? It seems Hillary and those conducting the hearings are correct. Even when caught in obvious lies, government spending tax dollars on these hearings is a waste tax dollars. Corrupt to the core.
Congress can not appoint special prosecutors.