#3 Sara
The Undertaker's then real-life wife, Sara was involved in a bunch of storylines with him in the early 2000s. Shortly after Vince McMahon bought WCW, top star Diamond Dallas Page was brought in and revealed as the stalker of The Undertaker's wife. The feud didn't go anywhere and DDP announced his retirement from pro-wrestling a year later.
By late 2002, Brock Lesnar had become the face of WWE SmackDown, after he won the WWE title from The Rock at SummerSlam 2002. Lesnar soon entered into a feud with The Undertaker, and made it personal with him by confronting his wife in the locker room on an episode of SmackDown. The Beast intimidated Sara, and then went on to defend the title on two occasions against The Undertaker on PPV.
At No Mercy, Lesnar and The Undertaker engaged in a bloody brawl inside Hell In A Cell, which ended with Lesnar defeating The Deadman to retain his WWE title, and thus establishing himself as the top Superstar on the blue brand.