#4 X-Pac (before)
At WrestleMania 14, Shawn Michaels lost the WWE title to Stone Cold and took a long hiatus due to his injuries. This led to Triple H overtaking him as the leader of DX the next night on RAW. Known as Syxx in WCW, Sean Waltman made his WWE return as X-Pac and joined Triple H's faction to a huge pop from the audience.
DX had already become one of the biggest factions in the industry by that time, and the new and improved version of the stable only helped its case. Waltman remained a strong mid-card act for the remainder of his WWE run.
#4 Scott Steiner (after)
Around two years after WCW's death, Scott Steiner signed with WWE in late 2002, debuting at Survivor Series. He attacked Matt Hardy and Christopher Nowinski at the event and was soon pushed to the main event in a feud with Triple H.
The duo fought for Triple H's World title at Royal Rumble and No Way Out, with The Game managing to come out with the title still secure in his hand. The matches were heavily criticized and this was it for Scott Steiner in terms of a push on WWE RAW. He was relegated to the mid-card for the rest of his WWE run.