In WWE Day of Reckoning 2, John Cena is pure evil when you fight him in the Story Mode. He will counter about 50% of your attacks, he never runs out of stamina, he can gain a full super bar off of 3 moves, and he can manage to get in 4 Finishing Moves off of one super charge. And this is a steel cage match, so if he manages to get the upper hand — and he will — there is no way to put any distance between you and him to regroup. Your only shot: throw everything you have at him and hope he doesn't counter, abuse restholds to recover your stamina, and once you've finally got him down, just pray that you have enough stamina left over to climb out of the cage. The final battle at WrestleMania, in which you must first fight Edge, and then battle Triple H in a Last Man Standing match with no health recovery whatsoever in between, is actually easy by comparison.
By some accounts, the SummerSlam Steel Cage fatal four way with Christian, Kane, and Shawn Michaels is far, far worse. All of the problems of the Cena match, with the added bonus of having to deal with three men at once instead of just one. Pure, unfiltered hell.
Less ridiculous but still noteworthy, one particular storyline in 'Smackdown Vs. Raw 2007' has your character defend a title belt against Batista... after getting your head bashed in with a pipe right before the match, translating to red-level head damage in game mechanics, and preventing you from even walking around the ring at normal speed from the get-go.
And approaching Perfect Play A.I. territory from 2010 is MISTER....KENNEDY at the end of Edge's storyline. Steel cage matches in this game are hard enough when the opponents don't stay down for long but KENNEDY adds to this by the aforementioned Perfect Play AI by countering damn near every move you throw at him making it impossible to build up momentum for a finisher that is your only chance at keeping him down long enough to escape... also if you take too long Maria comes down and opens the cage door when you try to go over the top forcing a brief Quick-Time Event to beat Kennedy else he wins and tops it all off with the reveal that Maria was on your side all along.
In Smackdown vs Raw 2011, the final boss of the Vs Undertaker Road to WrestleMania (The Undertaker himself) is extremely hard. In fact, the SvR2011 strategy guide says that he's the hardest opponent in all of the Road to WrestleMania.
Strategy Guide: "No matter what difficulty you play it on, this is a tough match. ... If you cannot reverse at least 40% of The Undertaker's attacks, this match is virtually impossible to win".
WWE 2K14 tops this with "Defeat the Streak" mode and Modern Undertaker. Yes, Retro Undertaker (aka 'Taker at the time of his debut) is tough, but he can be beaten if you persevere and manage to counter out of his chokeslams (which he uses to counter your pins if he's taken enough damage). Modern 'Taker? Counters pin attempts into the Hell's Gate submission hold, which—-if done enough times, can get you to red-level head damage in record time. If he counters into Hell's Gate when you already have red-level head damage? Just put down the controller—-you're NOT getting out of it unless you have the Resiliency ability (which you'll probably have already used to break out of a pin).