Hmmm what? AM outcarries LS? I always thought it was the other way around, specially factoring in LS usually build to abyssal. AM can get 6 slots faster than a LS can, but I don't think he outcarries LS.
AM will outcarry if he reaches 6items before naix(always) and given the right items. Might not win a man fight lategame, but he'll kill the enemy team faster than naix can kill him/your team. He gets trashed if you force fights earlier than that though, and depending on naix farm he'll get trashed regardless. I said "can outcarry" and not will outcarry, because it's not a guaranteed thing, same with spectre or void, both can but depending on the game might not. It's very possible for Void for example to chrono naix and not manage to kill him during the chrono, then Naix rages+abyssal void right out of the chrono and kills him while he's at low health, but assuming enough farm, void can just outright kill him during chrono then naix isn't a factor.
Naix is a great lategame but he's not super strong late and his farming tends to be a bit weak(midas helps a lot though, and so does infesting for farm), other carries assuming equal/superior farm will beat him late. With that said and I didn't mention that, Naix will tend to finish games a lot earlier. He's operational and deadly much faster than those other carries, basically get phase, drums(optional), armlet and you're good to go. Get a basher/abyssal from the kills, mkb if enemy starts stacking evasion for lategame, but basically at 20mins you're already a killing machine. In comparison the other carries I mentionned that can outcarry him are pretty much poop at that point unless insanely fed. Naix will crush them easily for the next 10-15mins. Even Weaver and PL aren't that good if they don't get a bit of space from the Naix to farm up, and if Naix gets fed towers/kills then it's gonna be over quick if he can rush an abyssal before you have proper gear.
In this case only Ursa does well, as he can crush Naix right away. There is however the factor that Ursa needs a bkb to deal with Naix's team CC, while Naix can just rage it out, so depending on team makeup, even Ursa won't do much(stuff like Rhasta or Lion fuck Ursa so hard before he gets a bkb, then you still have Bane, Enigma, Beastmaster etc). Oh on that note, those are good heroes against naix. Even with Rage, Lion can do a lot of work against Naix if he position correctly and/or have force/ghost. If you catch the naix in a cc chain and finger him, he won't be any trouble at all.