how strong is luke's lightning

Is there any canonical source that states how proficient luke was with lightning?

It could insta-kill a supposedly Force-immune slayer. Kyp Durron couldn't best even a slayer affected by the alpha red virus.

He doesn't do shit with his lightning in the Dark Nest trilogy, which is where the image is from. I think he attacks Welk with it?

I think the image was a cover to some book.

Edit: Yeah, like the great Neph said, and wait, he never used it? Had no idea.

No idea why they gave him lightning, though I never read the book, is there an explanation in it?

At some point Lukes order starts thinking that they should use the light and darksides since they're both sides of the Force blah blah. So they start using force lightning and chokes and shit until Luke gets uncomfortable over them torturing a dude with force lightning or something.

Ah I see.