When someone gets a raw burger and cant eat it and tells the manager what should the response be?

I would've called corporate

I just wanted a cooked REplacement burger. NOT REVENGE!!! HOLY!!!!

Yes you can

I cannot tell you what Wendy's ( or any restaurant for that matter ) will say, however, I would think they should happily take it back and offer you a more well cooked burger as raw meat is not approved for consumption. I have had even the most high classed restaurants make mistakes and admit to an error or mistake on the part of an employee. The fact is, NO ONE is perfect and that includes managers and owners. If they do not satisfy you, then let them know you are unhappy and will not return and will tell your friends of your experience. That should be sufficient for any civilized person and pursuit of further "revenge" is ridiculous. That is 'my' opinion only though, let your conscience be your guide.