Legion, Vulcan, Hyperstorm, Iceman Vs. Thanos
Team are all at their strongest height of power, for Legion, all his personalities are merged as one and he is in complete control of himself.
Vulcan is present day vulcan, but also with all the abilities and powers of all those he has ever had (all the ones he had borrowed stacked onto his current set).
For Hyperstorm, it is post battle with Galactus into the void, so he has full knowledge of all the events up to that point, with the benefit of being restored to the height of his power. (Well technically he never lost any power, I'm not sure where people got the idea Galactus enslaved him and was feeding on him. When galactus awoke from the void dimension, Hyperstorm arrived, the two battled and were both sucked into the void dimension.)
Iceman is at the level he was when he pwned Oblivion with a snow ball, nuff said (not but really just at his highest showing).
Vs.
Thanos, who is at his strongest, (no Heart, or IG, or cubes, just his own powers). Post resurrection.
Stipulation: Team is all working together, has 1 month prep, all resources at their disposal that they can get their hands on, and have full data about Thanos. Hyperstorm is leading their tactical planning, keep in mind he out maneuvered and out smarted both Reed Richards and Doctor doom combined when they had prep time vs him and he had none.
Objective: Can they kill Thanos?