Rage Shenron is the only Shadow Dragon in the anime who can take on his Super form without assistance, achieving the form through Electric Slime Body Build. Naturon Shenron takes on his form by absorbing a strong enough target, taking on his Super form in the anime through the absorption of Pan. Syn Shenron can transform into his Super form (named Omega Shenron in the English dub) by absorbing all of the other cracked Dragon Balls.
In the Dragon Ball Heroes: Victory Mission, Haze Shenron achieves his Super form thanks to Oceanus Shenron. Naturon Shenron also achieves his form once more through the absorption of Forte. Rage Shenron takes his on in an attempt to combat Super Saiyan 4 Broly but is defeated.
Video Game Appearances
Syn Shenron appears in his Omega Shenron form in most of his game appearances. All of the other Shadow Dragons who did not utilize a Super form in the anime achieve their form in the Jaaku Missions of Dragon Ball Heroes.
Syn Shenron's counterpart Xeno Syn Shenron has his own Xeno Omega Shenron form which resembles the Omega Shenron of the Cracked Dragon Balls but with a different darker color palette and Dark Dragon Balls instead of the cracked Earth's Dragon Balls.