The Undertaker
Along with Edge and Batista, The Undertaker made Smackdown must-see television for quite a few years. From the time the brand extension went into effect, to the time that it closed shop in 2010, the Phenom very rarely left Smackdown, and provided much needed legitimacy to a second brand.
Smackdown provided an outlet for a legend like the Undertaker to experiment (aka the “Big Evil” character). With and without the “Deadman” gimmick, he helped boost the careers of guys like John Cena, Brock Lesnar, Jeff Hardy post-tag team days, Edge, Batista, Randy Orton, and dozens more. Not to write him off as the ultimate enhancement talent; he’s also a 7-time world champion.
The smartest thing WWE ever did was to keep the Undertaker on Smackdown. Triple H and John Cena have dominated RAW for the past decade, and there’s no way he could have cemented his legacy in their shadow for all those years. Smackdown gave him a home to come and go as they liked. To put him up against main event talent and up-and-coming stars alike. To give him world title runs that boosted combined PPV events, but didn’t take away from the high-draw money stars like John Cena on RAW. Until he became a part-time star – right around the first match with Shawn Michaels – Smackdown was his home, and it was a perfect fit.