Berserker in Chinese / Japanese...

狂戰士 is the most popular way to write berserker in Chinese.

This title kind of means Norse warrior but often refers to the berserker in a fantasy role-playing game.
There is another way to write berserker in Chinese, which is 狂暴者.

狂暴者 is an alternate way to write berserker in Chinese.

This title often refers to the berserker in a fantasy role-playing game.

バーサーカー is how to write berserker in Japanese Katakana (phonetic Japanese).

Note: Because this title is entirely Japanese Katakana, it should be written by a Japanese calligrapher.

狂暴 is rage or the idea of going berserk in Chinese, Japanese Kanji, and old Korean Hanja.