I don't understand what the big deal is with the whole 3 chapters going on his side, not only did Huron capitalise on the confusion of what was really happening but the Chapters ultimately stayed loyal to the Imperium and didn't join him in his escape to the Maelstrom. Doesn't seem much of an accomplishment besides being a good liar or persuader to me. In terms of Abbaddon, the thing is the Chaos Gods are probably fine with Abbaddon "failing" each time as regardless of whether or not he wins, he sows discord, despair, and destruction in his wake; all of which cause more deep emotions to be invoked and usually followers, which only strengthen the Chaos Gods. As far as characte wise yes he's not exactly the most engaging but at least he has substantial fluff backing him up not to mention having arguably the LARGEST legion and may auxiliaries and allies that not only respect but (occasionally) obey his command. Huron is a paltry pirate lord in comparison and frankly to me is even more bland than Abbaddon. Game-wise he's probably one of the most boring SC's in the game whereas fluffiwse he just kind of popped out of nowhere flailing saying, "I'm cool! I'm special! I'm new! LOVE ME!", only to have his head vaporized by Kharn who then cuddles with kittens and eats a bowl of Khorne Flakes.