Gleeman Vox. He's definitely way more memorable and more threatening than Otto Destruct.
How about…
Sasha Phyronix v.s. Angela Cross
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Hmmm….I would have to say Sasha because she showed more love to Ratchet than Angela.
Try this one for size,
Giant Clank vs. Momma Tyhrranoid
Please notify me if Momma Tyhrranoid or any enemy like this is prohibited.
Giant Clank. He is the ultimate sauce in building bashing, mecha fighting combat. 
Note:
Yes, enemies like Momma Tyrranoid are allowed to be part of this versus game too.
Okay how about…
Dallas v.s. Sigmund
I choose him before and I'll choose him again and that is sigmund why? because I'm in love with that adorable robot 
dallas is ok but he's not my fave charatcer
Drek V.S. Dr.N
I choose him before and I'll choose him again and that is sigmund why? because I'm in love with that adorable robot
Drek V.S. Dr.N
I never knew Dallas was a female. I thought he was an obnoxious male announcer in Dreadzone all this time 
Just messing around Siggy, don't take it personally.
But anyways, I'll choose Drek over Nefarious. Drek had a pretty threatening and greedy scheme in the first game compared to Nefarious in UYA and in ACIT.
Okay, here's one:
The Plumber (the PS2 trilogy) v.s. The Plumber (the Future trilogy)
I never knew Dallas was a female. I thought he was an obnoxious male announcer in Dreadzone all this time
that's alright I relised I made a mistake as I forgot who dallas was at the time but I edited my last post to fix that mistake 
plus you're the second person from this site who calls me siggy (not that I mind though) but you can call me vicky if you like.
anyways I prefer the futrue Plumber because he's more friendly, cheerful, and nicer then the old Plumber don't get me wrong the old Plumber was a great character in his own time but he's quite grumpy back then
Courtney Gears V.S. Juanita
Alright Vicky 
Hmmm… it's kind of hard to choose this one because both characters DO have ATTITUDE and big diva personalities, but I would definitely choose Juanita over Courtney Gears. Juanita was at least hilarious and a fun character compared to Courtney, which I thought Gears was just one mean son of a… well you what I mean.
Oh I got one…
Carina v.s. Libra
I choose libra she made me lol when she had a deep man's voice and then crushes the can with her forehead (plus I forgot who Carina is at this time because having a poorly left ear is not making me think straight at the moment and it's making me feel a little moody 
)
Lawrence V.S. Al
Carina was the other Valkyrie with the French accent… or maybe Russian. I don't know, but it was either one of those. It's been a while since I've played A Crack in Time. 
Oh wow, tough choice there, but I would go for Lawrence over Al. Al is memorable yes, but he does have his stubborn picky moments that can annoy me sometimes. Lawrence has patience at least and if he doesn't like what he does, he can just humour us with his sarcastic quotes.
Shellshock v.s. Reactor
Shellshock because I lold when I saw the cutscene on youtube where he points out that Juanita is wearing Ace Hardlight underwear
Helga V.S. Thugs 4 Less Leader
The Thugs 4 Less Leader, which I like to call him Bob. I thought he was a pretty hilarious character in Going Commando, even if he wasn't a really bright character to begin with.
Sorry Helga, but you're still awesome though. :P
Ratchet v.s. Alister Azimuth
awwww crud I knew this was gonna happen sooner or later but I got to say ratchet cause I know him longer then alister plus ratchet has a big heart even if he gets stubborn or been a jerk sometimes although alister is an awesome character
but I feel sorry for the guy after 'you know what' has happend later on in CiT.
Clank V.S. Skidd
Oh nuts… I knew this day would come. I love those two so much, but if I had to choose one, it would definitely be Clank. He's one of the main casts in the series that's charming, fun and has a laugh you cannot forget. Skid is still awesome, but he can never win over Clank.
Captain Qwark v.s. Orvus
I pick Orvus cause he's funny in his own way …. even if his jokes are not always funny ^^; and at least he's not big headed like Qwark is
President Phyronix V.S. Novalis President
Novalis president because he's funny… I'm not sure why I find his paranoia funny, but hey. 
Skidd McMarx or Skidds Agent