What if Doctor Who teamed up with Elizabeth Comstock (Bioshock Infinite)

[StringfellowHawke]

Fully powered Elizabeth joins the Doctor as travelling companion. Who is the strongest character from any universe that they can beat?

[Nik Hasta]

With prep time, the Doctor is already a pretty unpleasant opponent.

With Elizabeth on his side he now has the ability to manifest pretty much any possible universe for any possible resources that he might need. He could even team up with parallel versions of himself, go to a universe wherein Gallifrey is at the height of its power and so on. Elizabeth, at her peak, is basically the "What do you need? You can have it," of prep.

In a straight fight with no prep however, both of them have conventional human reaction times and both are conventionally human in their durability so... like most speed based battle manga characters could destroy them pretty easily. Or suitable quickdrawing person with a gun like the Punisher.

[MichaelC]

Punisher better have a lot of bullets if he wants to put down the Doctor permanently.

[Twickster]

I'd count a regenerating Doctor as "alive and functional" given they're still generating offensive output. Given that tops out at "wiping out whole Dalek fleets from the sky", among other things, the person doing the quickdraw should be Hella durable themselves.