A group of thieves goes on smuggle drugs on a plane on an island only to find out it goes wrong because Predators want to destroy it.

"A group of thieves" = protagonist/s
"smuggle drugs on a plane onto an island" = main character goal
"Predators want to destroy it" = antagonist

While Avengers movies are one example of group protagonists, most story are written from a single character viewpoint. Decscribe the group leader. What has motived this individual to become a thief ? Perhaps we can sympathies more, if they have been forced into this dangerous situation of smuggling drugs to an island.

If by 'Predator', you mean that cool 80's film with Arnold Schwarzenegger, then oppositional character motivation is trophie hunting. But other predators exisit, usually motivated to plain old eat you a.k.a. Jaws. Usually the funtion of opposition is to expose character flaw. A couragous character (like Arnie in Predator 1987), when faced with a more powerful alien, casts fleeting moments of fear across his face. Nothing better than to watch a confident, tough guy shit himself momentarily, but then of course do something about it!