You can easily argue that The Undertaker is the greatest wrestler of all-time, given everything he's accomplished in his WWE career that's spanned three decades.
Never mind all those championships and many iconic matches, just think about how many times the man has been able to reinvent himself and how many superstars he was able to turn into legends.
There are plenty of feuds that helped shape up the icon that is The Undertaker, but even the best wrestlers are forced to work through some feuds and storylines that just never picked up any steam. Here are the five best and the five worst feuds of Undertaker's career.
10 Best: 'Stone Cold' Steve Austin
The Undertaker and 'Stone Cold' Steve Austin were two of the central figures during the Attitude Era. Without either guy, it's safe to wonder if WWE would have lost the Monday Night Wars.
Though Undertaker had many great feuds during the Attitude Era, his rivalry with Austin really stands out. There was that segment where he "sacrificed" Austin by raising him high above the stage at one point. These two legends clashed at numerous pay-per-views as well, including SummerSlam 1998, No Mercy 1999, Over the Edge 1999 and Armageddon 2000.
Any time these two clashed in the ring, it was a sight to behold. Fortunately, we got to see plenty of it.
9 Worst: Giant Gonzalez
The Undertaker's feud with Giant Gonzalez (billed at around eight-feet tall), started at the 1993 Royal Rumble pay-per-view when the latter eliminated The Phenom - which helped Yokozuna eventually win the event.
Undertaker got a chance at redemption when he faced Giant Gonzalez at WrestleMania IX. Unfortunately, the entire match itself was lacking in pace and creativity, and the ending was even worse: Gonzalez was disqualified for using chloroform to knock out The Undertaker. This entire show is widely considered to be one of the worst in WrestleMania history, and this match was a prime example of why.
Their feud finally ended when Undertaker defeated Giant Gonzalez at SummerSlam later that year.
8 Best: Edge
Undertaker and Kane (Brothers of Destruction) had a brief feud with Edge and Christian in the Attitude Era days, but it was Taker and Edge's singles feud several years later that took the WWE Universe by storm.
The feud started when Edge (who had won Mr. Kennedy's Money in the Bank contract) cashed in to become the new World Heavyweight Champion on the May 8, 2007 episode of SmackDown - after Mark Henry brutally attacked The Deadman.
Undertaker then took time off to recover from an injury, but he was able to win back the title against the Rated-R Superstar at WrestleMania XXIV, in arguably one of the best matches in the show's history. Undertaker had successful title defenses against Edge at Backlash and Judgment Day before losing at One Night Stand.
7 Worst: Sid Vicious
Sid Justice was one of Undertaker's first feuds back in the early '90s. They first met at the 1991 King of the Ring event, and they clashed numerous times throughout January of 1992.
Sid returned to WWE in 1995, following a stop in WCW, with a new ring name "Sycho Sid." Sadly, there wasn't much to love about this rivalry, and their World Heavyweight Championship bout at WrestleMania 13 - won by Undertaker via pinfall - was considered a massive disappointment.
The in-ring chemistry just wasn't there between the two stars. Simply put, there was just way better feuds for both superstars.
6 Best: Mankind
The Undertaker deserves plenty of credit for his job in building up the legend of Mick Foley/Mankind. These two put together one of the most illustrious wrestling rivalries, which spanned from 1996 to '99.
The most iconic moment of this rivalry took place at the 1998 King of the Ring pay-per-view, where Mankind took two dangerous and life-risking bumps off the top of the cage. That marked the beginning of Mankind's iconic status.
Undertaker and Mankind clashed time and time again during Raw Is War as well, and there was even a feud involving The Phenom and Big Show against The Rock 'n' Sock Connection for the Tag Team titles.
5 Worst: The Great Khali
Great Khali debuted for WWE in 2006, and his first rivalry was against The Undertaker. The company gave him a major push right away, and Khali had some promise in his early days. After all, few people could match or top Undertaker size-for-size.
Eventually, it became evident this rivalry wasn't going to work well in the long run. Their matches had an extremely slow pace and almost no "wow" moments. It's no surprise that their feud only lasted a short period.
Great Khali defeated Taker at Judgment Day, before the Deadman returned the favor in a Last Man Standing match on the Aug. 15, 2006 episode of SmackDown, thus ending their feud.
4 Best: Shawn Michaels
The two icons would then clash at WrestleMania XXV in what is widely regarded as one of the greatest matches in WWE history. Just when it looked like Michaels was about to end the Undertaker's perfect streak, The Phenom narrowly escaped with a pinfall victory.
Fans got an encore one year later at WrestleMania XXVI. This match was just as good, if not better, than their previous bout. Finally, Undertaker put away Michaels to extend his streak to 18-0, and the latter retired (per the match stipulation) after piecing together another prime WrestleMania moment.
3 Worst: Diamond Dallas Page
It doesn't usually end well when WWE brings a wrestler's personal life into a storyline, and this was the case during the Undertaker and Diamond Dallas Page feud in 2001.
DDP arrived from WCW and began "stalking" Undertaker's real-life wife, Sara, in the storyline. Even during the anything-goes days of the Attitude Era, the whole angle was quite disturbing and very difficult to watch.
Their feud carried over to SummerSlam - where Undertaker and Kane defeated Chris Kanyon and DDP to become the new World Tag Team Champions.
2 Best: Kane
The Big Red Machine was repackaged as "Kane," and the character debuted at the 1997 Badd Blood: In Your House pay-per-view. Paul Bearer had previously warned Undertaker that he was coming.
Kane - billed as Undertaker's half-brother - interfered and helped Shawn Micheals defeat Undertaker in the match. This started up a rivalry between the two legends, and they formed one of the top storylines of the Attitude Era.
These two superstars added more elements of horror and darkness that were perfectly suited for the Attitude Era. Undertaker was an established main eventer at the start of this rivalry, but he was instrumental in helping the legend of Kane grow. By the way, that whole Brothers of Destruction tag team was pretty cool, eh?
1 Worst: Heidenreich
The Heidenreich character was controversial from the beginning; he was involved in some disturbing segments that should have never made it to TV. WWE portrayed him as a "psychopath" who took pleasure in viciously assaulting those who stood in his way.
Even the legendary Undertaker wasn't able to help build up his character. They feuded after Heidenreich cost him a WWE Championship match against JBL at No Mercy 2004. Undertaker scored numerous victories against him, but Heidenreich continued to hold off The Deadman in his WWE Championship pursuits against JBL.
Undertaker was able to defeat Heidenreich (with some help from Kane) in a casket match at Royal Rumble - finally putting an end to a feud that just never developed that much momentum or entertainment.