#1 Drew McIntyre
Drew McIntyre is one of the biggest names in the WWE today, and if they intend to give him a true main event push following WrestleMania 35, then retiring the Wrestling Machine is a great way to start that off right. Drew has been feuding with Kurt over the past few months, and with his intense attitude and willingness to work harder and be the best, he's the perfect option for Kurt's final match.
Drew also doesn't have any other match lined up at WrestleMania, so unless they want one of their top main event stars in the Andre The Giant Memorial Battle Royal, then this one begins to make even more sense. Ideally, most legends would be willing to put over a future star in their final bout, and while that applies to 3 out of the 4 options on this list today, McIntyre makes the most sense, and I'd be shocked if this wasn't the way that WWE went.