Thor has been around since the very beginning of Marvel: Avengers Alliance. What's amazing about this character is that he is still the most potent sweeper in the entire game. He may not have the highest attack power among all the heroes (although it is pretty high already), but he does have the most powerful area attack in the entire game: Summon Thunder.
Since Summon Thunder is so powerful and it has the Catastrophic property, which prevents protection, avoidance and always hits, you can build a whole strategy around this move.
Now, Thor is not a very versatile character. You will always use him in the very same fashion: Inspire Bravery, Empowering Strike, then Summon Thunder. This, however takes too many turns to setup and characters like Ghost Rider, Phoenix and Magik can negate the stacks of Might of Mjolnir with Soulfire. Basically, the Classic Thor costume is useless. You need to have the Modern Thor armor, since it begins every match already with the two stacks of Might of Mjolnir.
This Modern Thor costume comes in two classes: Bruiser and Blaster. I prefer Blaster since it can decimate any opposing Bruiser, which are otherwise very difficult to deal with because of their high Heath and Defense stats. You may be able to attain ridiculously high Attack power with an Enraged Bruiser. However, I don't recommend the Bruiser costume for two main reasons:
1) Bruiser are often One-Hit-KOed by opposing Blasters.
2) Enraged stacks can only be obtained by attacking or being attacked by an opposing Scrapper, which is kind of difficult to achieve since Scrappers are often protected by other heroes or by an Agent's Protect effect. Also, the Enraged stacks are kind of slow to obtain, and you want to use Summon Thunder as soon as Thor gets his first turn. Finally, Enraged stacks are kind of an overkill since most teams will anyway resurrect after a successful Summon Thunder attack. In other words, you don't need sky-high attack power. You just need reasonable status boost to make Summon Thunder lethal. This is why Enraged stacks are usually unnecessary.
With Modern Thor the strategy is ridiculously simple, yet incredibly powerful. You basically fire off Summon Thunder as soon as possible. If you do this, however, you will find that it does take a gigantic chunk of health off the entire enemy team, but it will not kill them. Besides high Defense stats, there is also the Deathwatch effect from Phoenix and Valkyrie and the item equivalent: Hoarfrost Mace and Odin's Staff. Said items are not that popular anymore, but Phoenix and Valkyrie are both very popular characters in PVP, so they may hinder Summon Thunder's sweeping ability.
1) You can another Might of Mjolnir stack by making an Empowering Strike. You may do this when the opposing party still has some kind of resurrection effect. You will need to make minor attacks with your Agent and/or your other hero to "kill" your opponents and trigger their resurrection ability. After they are triggered once, they are ready to be killed again for good.
2) You can unload Summon Thunder again since even with only one stack of Might of Mjolnir the attack becomes lethal since the opposing party is already greatly weakened and Thor also has Strengthened, which arguably makes up for the second stack of Might of Mjolnir. You may unload Summon Thunder with only Might of Mjolnir stack only if the opposing party does not have some kind of resurrection effect. In that case, resort to option #1.
Summon Thunder Optimization
Since your whole strategy revolves around unloading powerful Summon Thunder area attacks as soon as possible you want to do one of two things:
1) Give Thor an additional action from another hero, like Cable, or from your Agent, so he may use Summon Thunder before an enemy gets the chance to apply Soulfire of use Scroll of Angolob to remove all of Thor's Might of Mjolnir stacks. If you use Cable as Thor's partner, you get to have two very powerful offensive heroes in your party, but then will end up with two Blasters, which is not recommended at all. Every team needs class variety so it may have better coverage of both its enemies and its very own weakness.
2) Give Thor even more Attack power boosts with your Agent or with some other hero, like Emma Frost. Those who were lucky enough to obtain the Cosmic Flame item from Magik's Special Operation can use it to both boost Thor's attack power even more and apply Soulfire to the opposing party with his next attack, which should be Summon Thunder. If you don't have the Cosmic Flame, you can use Emma Frost's Unlock Potential, which greatly increases one character's stats for a single turn. She also has the ability to weaken your enemies attack power with her area attack, Mental Trauma, which inflicts Migraine, or finish off aggressive characters that don't have any support move with Psychic Tap's Mental Anguish.
I prefer Emma Frost over Cable since her Phoenix Five costume has a very helpful passive ability: Phoenix Potential: Cosmic Power, which randomly removes any harmful status ailment and boosts your characters power. I also like her because her psychic attacks trespass shields and protective abilities. Her Mental Trauma area attack is also useful to finish off a weakened opposing party after Thor's Summon Thunder. Better yet, if he gets hit by Soulfire or Scroll of Angolob, you can change your strategy to Psychic Tap and Mental Anguish damage while Thor builds up again his Might of Mjolnir stacks. Even more, popular heroes like Wolverine and Hank Pym can remove the Protect ability from your agent (in which I will elaborate in a minute) and will leave Thor vulnerable to following attacks. In that case, you can use Unlock Potential on your Agent to restore his Protect passive ability. Finally, you want a Tactician Emma Frost in case Thor's strategy fails or gets delayed. You need to be able to put Mental Anguish in as many opponents as possible, and a Tactician can do that when there is a Blaster in your opponent's team.
Although Cable may enable Thor to fire off Summon Thunder faster, I think it is pretty clear why Emma Frost is the better teammate over Cable.
The AgentYou may have noticed that Thor is the Backbone of your strategy, so you really want to protect him at all cost. You need your Agent to fulfill the Tank's role.
I don't recommend using a Bruiser costume on the Agent since he will be tanking most attacks from the party and any Blaster can potentially kill him with only one attack. A Blaster costume is not recommendable either because Thor is already a Blaster and and having two characters in your party with the same class is not a very good idea. I recommend equipping your agent with a Scrapper Power Armor. Bruisers may get the Enraged bonus off your Agent, but Thor's Blaster class bonus will destroy it even with the two Enraged stacks since Blasters completely ignore a Bruiser's defense stat and always critically hit them. As a bonus, you get to attack Infiltrators twice.
For the Equipment you need items that give your Agent the Protect passive ability. Hoarfrost Mace if very nice for this and it combines nicely with Nanite Inductive Nailgun, which randomly creates a shield around the Agent and performs a counterattack. You may also consider the Signpost to regain any lost Health. This item is very helpful for tank Agents. The last item is up to you. I like to use Dark Sigil to ensure a critical sweep from Summon Thunder and leave residual damage to kill any surviving opponent. You also like to use Warbringer Axe for two reason's:
1) It further boosts Thor's attack power.
2) It is the only powerful attack that your Agent can make since both Hoarfrost Mace and Nanite Inductive Nailgun don't have a very high attack power.
The TeamAgent (Scrapper Power Armor)
-Nanite Inductive Nailgun
-Dark Sigil or Warbringer Axe or Cosmic Flame
Thor (Blaster Modern Thor)
Emma Frost (Tactician Phoenix Five)
Another particular thing that you need to do with this team in order for it to be succesful in PVP is to maximize your PVP bonuses to the Attack stat. In other words, put a Blaster alternate costume on every possible hero and level them-up to Level 12. This will increase your attack power incredibly on PVP. Of course, this is easy to say, but it actually takes an enormous amount of time and resources to make everybody a Blaster and level them up to Level 12. Still, this is the most important detail for a Thor + Emma Frost team to succeed.
Try this powerful team and tell me how it goes!