Antvasima and Matthew, please read this.
In response to Matthew saying Dante beat Abigail in base:
In Redgrave's video Dante's voice changes into a demonic voice at about 15:50. Redgrave's right. The voice clearly changes and then energy erupts.
Here's another video.
https://m.youtube.com/watch?v=bw8UswJlo68
At 1:30 you can hear Dante's voice change and you can hear the snarling demonic voice while Dante's crushing Sid. That is what his Devil Trigger sounds like. It also accompanies a burst of red energy and electricity.
And here is a video of the Japanese version with non-English subtitles (sorry about that)
https://m.youtube.com/watch?v=h4CDdUEiMRQ
At about 7:40 his voice change also happens, and in the Japanese version it is a lot more obvious.
And here's Japanese with English subs.
https://m.youtube.com/watch?v=l_TqBlQGxrY
In this one his voice changes at 3:30. It is very obvious.
This makes it clear he did use Devil Trigger. And it isn't Abigail's voice; Abigail's Japanese voice is heard near the start of the video and sounds absolutely nothing like that.
Now, ultimately the insistence that it's an outlier is currently built on Dante being able to keep up with Mundus in base and Abigail being Mundus level. First things first, keeping up with Mundus.
Many Devil Arms do enhance the wielder even without Devil Trigger, including two stated to enhance speed.
These Devil Arms are Alastor:
http://static.comicvine.com/uploads/original/11113/111130453/4643064-alastor1.png
And Beowolf:
http://guidesmedia.ign.com/guides/640426/images/beowulf.jpg
This proves Devil Arms can enhance physical abilities with their magic.
And if the sword Sparda wasn't enhancing him he could never have harmed Mundus and certainly couldn't have withstood his attacks, and afterwards when he doesn't have it Mundus laughs at him and calls him weak.
And for proof he can still take Mundus's attacks, here is another video:
https://m.youtube.com/watch?v=8Ti1ot6ABdA
At 0:14 the projectiles prove to be able to somewhat damage Sparda Devil Trigger Dante. And at 0:27 he reverts to base and is getting hit with the projectiles still. You can see several go off right next to him with the blasts hitting him, and one appears to hit him directly, all while he's in base. On top of this he can of course withstand his attacks in gameplay.
And for Abigail:
Here's an explanation for why in DMC demonic power being wielded by a lower creature has consistently been demonstrated to be incomplete. Following is a video of Arkham.
https://m.youtube.com/watch?v=8tsNZkAdBko
At 3:06 Vergil states Arkham can't control Sparda's power, and at about 0:40 Dante proved it by blocking Arkham's attack. They then proceed to beat him.
Bear in mind Arkham was more powerful than Sid to start with.
Sanctus was the same in DMC 4. Here's a video of Sanctus while wielding the Sparda sword. Note he does have a connection to it. He isn't just wielding it, it's why he looks like he does here.
https://m.youtube.com/watch?v=Xpp1YagAibM
Dante laughs at Sid's power, and there's no instance of an unworthy demon stealing power in DMC and getting all of it; they invariably turn out inferior to the original. What's more the original Abigail could have easily been weaker than Sid implied. Overall it seems a bit of an assumption to assume he's on Mundus's level.
As a final note, if we still say Abigail is Mundus level it won't make an outlier of the feat, since Devil Trigger is how Dante beat him.
https://mobile.twitter.com/PG_kamiya/status/755217839951187968
Above is confirmation Devil Trigger is a big boost and not a small one.