Spartan Throne recently started a new series called Sparty Tech that will showcase quick strategies and combos in Ultimate Marvel vs. Capcom 3. The first episode, Big Boy Combos, shows off two combos that can kill much of the cast. The first combo starts from a Magneto air-throw, and uses a raw tag to Doctor Doom and a THC to kill Hulk. The second uses Iron Fist and Dormammu to kill Thor off a basic crouching hit-confirm.
Both of these combos are practical and able to be performed with match start conditions, but they also require very specific team setups.
Source: Spartan Throne