I had trouble removing the locknut from my Delta faucet so I designed this simple tool to make the removal easier. I printed mine w/ 2 bottom layers, 4 perimeter and 4 top solid layers w/ 75% fast honeycomb infill.
This is what the locknut looks like:
https://www.homedepot.com/p/American-Standard-Mounting-Nut-M906617-0070A/205506584