I use step ups to bring up my weak leg.
I just stack some cinder blocks and viola! I am past parallel.
You can do them with dumbells which provide a deadlift effect, or you can use a barbell and go heavy.
The hard part is keeping the form the same throughout the set. Eventually you end up bouncing on the other leg for assistance , which may or may not be a bad thing.
I think they work great.