The 'burden of proof' is on the plaintiff, since the defendant is presumed innocent until proven guilty. [=the plaintiff must prove that the defendant is guilty]
The 'tax burden' has been falling increasingly on the middle class. [=middle class people have been paying a greater portion of taxes]
For the rest of his life he 'was burdened' with the knowledge that he had done nothing to help them.
(..) It is time for their secret identity to become their only identity. Time for them to join us, or go away. Under public pressure, and the financial burden of an ever mounting series of lawsuits, the government quietly initiated the superhero relocation program. The supers were granted amnesty (..)2004 The Incredibles