The deficit stiff-leg deadlift, where you stand on a platform, was my go-to lift for improving the convention deadlift for powerlifting. And it's possibly one of the best overall posterior chain developers ever.

Deficit Stiff-Legged Deadlift

A lot of people think of this as a hamstring move, but if you're going heavy you'll know the brutalization they cause for the erectors, lats, and entire upper back. This is a total back movement. When your strength on this lift goes up, don't be surprised when your deadlift goes up right along with it.

I use a mixed grip but if you want to do these with a hook grip or straps to balance out that pesky twist in the spine that comes with a mixed grip that's okay too. Keep the reps on the low side. Once fatigue sets in, it's easy to get very rounded and end up with too much spinal flexion.