Getting rid of hop, especially a low spot, is the hardest thing to do when aligning a tight wheel. Unlike wobble, hop requires the rim to move along the circumference because higher radius implies longer circumference. That means that when you bring a hop in the extra material needs to be spread along the entire circumference, against the resistance of the other spokes.
1/4" is quite a lot, and I wonder how it got there in the first place. Pulling it down will require staggering tension, and will also cause tension unbalance as the material tries to flow out. I suggest you carefully lower the overall tension by degrees, working about 1/4 turn at a time, until you're at about half tension. Then you can work on the hop, getting the wheel round, and tension fairly even before reloading back to normal tension by degrees.
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