Lua script that not only lets you adjust the name of difficulties, but also the descriptions and masks accompanying.
Built on top of Epitaph's "Death Sentence to Overkill 145+" mod using Snh20's "string_id Revealer."

This covers not only the difficulties as displayed in Crime.Net, loading/difficulty screens (works with certain loading screen animations), but also the difficulty masks, achievement names, descriptions, and unlock requirements.

By default, I've adjusted Normal, Death Wish, and Death Sentence to be Mod Testing, Overkill 145, and Overkill 145+ respectively, all other difficulties have been unchanged. I've commented out unused lines, just delete the double minus at the start of the line to enable them.

There is now a Vanilla download option with everything uncommented, if you wish to rework all from the beginning.

If you wish to reupload your own set, be sure to credit Epitaph and myself.