Ajax

Let's get this out of the way "“ as Ed Skrein has said, his version of Ajax was just an early version of the villain (an early and cost-effective one, that is). And, as we all saw, Ajax actually died at the end of Deadpool. But did he really?

In the comics, the two have battled it out a couple of times; on one occasion, Deadpool seemingly killed his enemy. But, as it was later revealed, Francis survived, and came back with a vengeance. And this time, he wasn't just using his super strength, increased agility, and accelerated healing. He also received some implants to make him even more dangerous.

How dangerous? To put it simply, he managed to defeat the Merc with a Mouth several times, before having his neck snapped.

So yes, Ajax would be great for a second outing. Furthermore, he might have a personality this time around.