Lich King > Illidan >>>>> Grom.
Grom is totally outmatched. We already know how it goes when warriors fight magic users, which both the Lich King and Illidan are. When Grom killed Cenarius he had an army, and the two times he killed Mannoroth he wasn't alone either.
Why is Illidan's over-confidence and arrogance excuses for him losing? He's lucky Arthas didn't care to finish him off. The strongest doesn't always win the battle, because it takes more than raw power alone to win a fight. Illidan is indicative of that. If he toyed with his opponent, that's on him. Even if the argument could be made that in re-match, Illidan would win, Arthas' power grew exponentially after their duel, so that duel, which Arthas won, the power levels don't apply here. Here, it would be Lich King Arthas vs. Illidan, which I still believe LK Arthas takes it.
Lei Shen > Legion Illidan <(this could still go either way)> Lich King Arthas > Chaos Grom
Subarashii chin chin mono
Kintama no kami aru
Legion Illidan > Lei Shen > LK > Grom
You forgot how little effect magic can have on Illidan. You must realize his history as a super powerful mage, before becoming a Demon Hunter. Lei Shen could put up a fight, but Illidan really has more at his disposal and overall, more power.
Gkrom killed Cenarius 1x1
Like Mannoroth in Warcraft 3, Thrall did nothing important.
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Again. The Lich King completely restored his powers and gave up almost all of his powers that he(Lich King) had. This Arthas was not weakened. This Arthas was much stronger than ever before.
this is not rly a fair fight
a fair fight would be theey in WC3 era, and i would give Grom>Arthas>Illidan
According to Chronicles the 2 were evenly matched. While it should be assumed that they both gained more power, Arthas pushing out Nerzhul to become the Lich King, and Illidan having his Outland shenanigans. I'd continue to say they are evenly matched. Really it would depend on where the fight was held that would determine who would ultimately win. LK is stronger near his throne and Illidan would gain a boost around fel.
Magic wise I think it would be a bit of a wash, the LK armor is made of saronite which is resistant to pretty much all magic and I swear the area with saronite was chosen specifically by Nerzhul because it was fel resistant as well (I might be wrong here, I'm having trouble finding sources).
Lk vs Illidan wise, it's still a wash. While Illidan as a magic user knows shit about death magic, Demons do know of it because of the Nathrezim.
I don't really know why Grom would be here, his main feats are against pitlords and killing them is kind of Illidans schtick.
Chaos Grom ez diff. He is simply stronger. One hit and Arthas bones would be crushed. Same with Illidan but illidan at least has agility. Though, according to lore, Grom also was very smooth and agile orc. So it would compensate.
IF Illidan can get his head out of his ass and not show off? he might stand a chance... though his 1v1 with arthas WAS when Arthas was at his weakest, almost dead, drained of power and on a timer before he was done anyways.... So something more like what we saw when Arthas was bringing the scourge to wipe out the world? I'm not sure Illidan would be able to do much beyond dance around and hurl insults.