Rivalate is not wrong though and it's understandable how they came to the conclusion of Rivalate.
In Japanese, リベレ一ト is the word for Liberate. However, the weapon is リバレイト, which is decidedly different, so the translators realised that translating to Liberate would not actually be correct. The weapon name is most certainly based off the word Liberate, but it is not an exact match, and the English translation reflects that.
While I do think Rivalate sounds decidedly worse than Liberate, it is not wrong by any means. There's many issues with the translation, but this is not one of them. Basing your knowledge of the localisation off the fan patch and then criticising it is not a good look.
As for the potential, the potential is not in Katakana (the phonetic alphabet), but rather it's in Kanji: 解放の牙, which translates as Liberation's Fang or something similar.