How do I repair deck sloping on one side of the house?
I had a deck where the rim joist bowed out, and the cross joists came unattached.
I used two car jacks to get everything back up to level to be reassembled and use proper joist hangers.

Safety tip, use the jacks to lift, but once up, set a stack of lumber or blocks to hold it up while working underneath.  If you have some 4x4 stock (or 2 2x4s edgewise), don't lift a specific joist, but use a cross piece to lift several and spread the force.