#1 Brock Lesnar

Believe it or not, Brock Lesnar might not be champion right now if it wasn't for Baron Corbin. In fact, it was Corbin who ambushed Bruan Strowman and helped Brock Lesnar gain the upper hand on him to win the match. Ideally, that should mean Lesnar's win is ruled invalid and his title vacated thanks to the interference
Of course none of that will probably happen, but not doing so seriously hurts the legitimacy of the belt and creates a situation where Brock Lesnar is once again champion when he shouldn't be. Beyond that, Lesnar now has to deal with Strowman alone at The Royal Rumble, which could be difficult thanks to the authority now being on the fan's side.
With that being said and fans not wanting a part time champion anymore, its very likely that Lesnar will lose the title sooner rather than later, which is another big way Corbin's exit will impact the Raw roster.
In the end however, Lesnar could still power through all this to keep the title for quite a while, but if it's not what the fans want, there's probably not much chance that it will happen.
Becky Lynch has been challenged HERE.