“Ardent / Violent / Vehement / Furious” in Japanese is 烈, read retsu, hage (れつ, はげ). It is a Jōyō kanji taught in Japanese secondary school (junior & senior high) — the 高手 · Master tier beyond the grade 1–6 Kyōiku set, and appears in words such as 激烈 (violent).
What does 烈 mean?
Same sound, different character — the classic trap. Compare them side by side: