Asgardians vs. the MCU
Hela has been able to convince Loki and Thor to join her cause. They decide to conquer the 9 realms starting with Earth. The three Odinspawn siblings arrive on Earth together with Sif, Valkyrie, the Warriors 3, Skure and the Destroyer. All of them are in standard gear and at full power (Thor has Mjolnir, Loki has Gungir). Heimdall stayed behind to operate the bifrost.
Earth sends every single earth-bound MCU hero to fight the Asgardians. Dr. Strange uses the time-gem to go back in time and save deceased heroes from dying (like the Ancient One and Quicksilver, etc.) so they can join the fight... but this leaves the time-gem out of power and cannot be used in the fight itself. The GoTG were also vacationing on Earth when this happened and get involved in the fight against the Asgardians.
Only earth-bound heroes and anti-heroes join in the fight (plus the GoTG), no villains or extra-terrestrial/extra-dimensional beings. The MCU heroes are all armed in standard gear.
Dr. Strange and the Ancient one can use portals to teleport people around but the Asgardians can also ask Heimdall to teleport them around.
Can the combined might of the MCU's Earth heroes stop the Asgardian strike team?