Even a regular Striking Scorpion has killed an Ork Warboss, not really fair to put them against the greatest of the Eldar.
Well...don't know how it would play out. I do know that; In the path of the eldar series, in warrior, karandras is killed by a dreadnought. Korhandril does take his body over in the end. Ork war bosses are sort of a toss up, depending on how much they fight and win. The more they fight, the bigger they get and the stronger they get. Ghazkul is reportedly 14 feet or more, with some ork war bosses being probably even larger than he is. So can an ork warboss take on a dreadnought? If so, one would surmise he could at least kill karandras. It would also depend on which Phoenix lord was fighting, since they all have various abilities and strengths, weaknesses and what not. Since Phoenix lords are basically special characters, one would assume they would fight an ork special character, like ghazkul. Somehow I think ghazkul would win. Been awhile since I've played tabletop and busted out some math hammer, but I don't think the Phoenix lord would be able to get through the high armor/toughness +eternal warrior. That's if we're talking table top. Edit: against Phoenix lord Jain zar I don't think much would stand a chance. She can basically take out abbadon, Dante and several other characters considered the best melee characters in all of 40k, so I think she would have the upper hand.
Well if the Phoenix Lord is facing The Beast, my money is on the ork. Any other boss would probably lose, but it does depend on the individual ork.
To expand on that point, look at this guy: He has a string. Who the hell brings string to war? Nobody's ever fought and won a battle with a piece of string! Now the bayonet on the other hand; The bayonet has seen extensive action in many, many wars throughout human history! No doubt it sees much more use in the 40th millenium. Because the bayonet has many proven victories, and the string has like, none, the guardsman with the bayonet is clearly using a vastly superior weapon, and would win in a fight easily
WELL AS I'Z REMEMBER A SILLY GROT ONCE KILL'D AN ELDAR RUNT, RUNT ELDAR ARE ESSENTIALLY STILL ELDAR AND ANY ORKBOY IS STRONGER THAN A GROT AND WARBOSSES ARE EVEN STRONGER DAN DAT. SO ANY WARBOSS COULD KRUMP ANY SILLY FIRE BIRD LORD, IT'S JUS SIMPUL LOGIK, THO TO BE FINKY, ORKS ARE THE BESTEST THERE IS, A GROT COULD PROBABLY EVEN KILL DEM SILLY CHAOS GODS. I'Z KRUMPED ALL THE BLACK AND THE WHITE LIBRARY BOOKS SO CLEARLY I'M A RELIABLE SAUCE. LIKE TOMATO OR SUMFING.
Generally speaking: Waaghboss should be no match for a phoenix lord. But a Waaghboss draws a lot of power from his surrounding Boyz. If enough orks are there, and they all think their Waaaghboss can beat that pansie, im not too sure... 1v1 Is not a question. But a waaghboss facing a Phoenix Lord with all his boyz backing him up...? Maybe Ghazgkull would be an equal match
If the warboss in question has been fighting ELDARI (I know u love it) for a while, has some kuztom shield and cibork bits here and there, I bet my teeth on the green fella. Usually, from the books I read so far, this kind of warboss is defeated by some deus ex machina crap that distracts the ork long enough for someone to thrust a pointy object in his face. Hence I would think a warboss like this has good chances of beating the living zog out of a phoenix lord in 1v1.
Wouldn't reading ALL the books actually cause problems with lore interpritation? Too many sm scouts killing hordes of orks with knives and that kinda crap out there for me to consider a lot of the lore to be "accurrate". Like that time 2 harlequins killed like 30 custodes INSIDE the imperial palace kek.