#2. The Undertaker

Surprisingly, The Undertaker has also not been added to the WWE RAW Reunion show, considering he was on WWE television just a few weeks ago at Extreme Rules.
The RAW Reunion show could be the perfect place for The Deadman to set-up his next feud, which would eventually result in a match for the SummerSlam PPV, which will happen next month.
Breaking Vince Russo and Jim Cornette update HERE.
The Undertaker's last feud was against Shane McMahon and Drew McIntyre when he teamed up with Roman Reigns. I think that The Deadman could maybe have a feud with Elias, which WWE have been teasing for quite some time now.
Elias attacked Undertaker at Extreme Rules during the tag team match, while he has also teased a potential match with Undertaker in his various songs, where he has taken potshots at 'Taker. It would be an interesting match, one that would certainly help Elias' career.