Catachans are a huge exception to this rule. It may have been propaganda or biased, but an author wrote about a single Catachan guardsman taking out a Warboss! Catachans are and always will be the most badass and scary regiment in the Imperial Guard. Amen. Oh, wait, this is the Ork forum. Dem catahan's got real proppa foights!
But that was probably Sly Marbo, right? This guy is the Chuck Norris of 40k so it doesn't count! There's also stories of guardsmen blowing a Chaos Marine's head right off (through the helmet and all) with his lasrifle, or one out-stealthing a Mandrake. I wouldn't take any "fluff", from Codex or novels, too seriously. And since we're on the Ork forum, Armageddon Ork-hunters > Catachans.
There are plenty of bad ass IG units that can do some crazy stuff, but the vast majority of IG are not these guys. I feel like many of the books that show IG as their main focus do a good job of highlighting IG strengths and weaknesses. They throw in ass pulls now and again but they aren't ever bad enough to make me dislike what I'm reading...unlike almost all SM books and their insane luck/happen to have perfect magic mcguffin on hand plot shenanigans they pull.
Ciaphas Cain kills a warboss with a las pistol in a funny but beliveable way. Boss was toying with him because he couldn't really do much so Cain says screw jumps at it, ork laughs, and Cain jams the gun barrel THROUGH his eye and then unloads on its brain. Imo that is awesome and beliveable while still showing orks in a good way.
For a good reading about IG the Maccharius novels are quite good. It show you the way to become a hero and how many die before.
