Phantasy Star IV (Genesis) - Boss 18
Gens v2.12 Movie 11
Chaz - level 45
Rika - level 48
Rune - level 41
Wren - level 42
He could be more difficult, I know he can use Legeon or Tandle, no idea why he did not.
Don't forget Sa-Lews is not evil, he (or she?) is an agent of the Pure Light who is testing you, so holy magic such as Efess will be ineffective. He's also immune to fire magic such as Nafoi or pure physical attacks such as Nazan - note that most advanced weapons you use at the end of game don't do physical damage but another king of damage often called "radiation damage". Rune's Legeon also does radiation damage. Pure energy damage does harm him but is not as effective as against evil bosses, so best Chaz' attack is Crosscut.
Yes I know, I am telling exactly the same thing in the description of the previous video, but actually you could do this boss first if you want, so I have no idea in which order ones will read the video descriptions. At least you are reading them, I am afraid not everyone does.
It seems to me he uses only magic attacks, so I did not launch Deban.