Best teams for 3* and 4*?

For 3* PvE I use Strange/Fist/Daken (2 or 3* version) esp if Daken is a slightly higher level.

Daken tanks Purple/Blue/Black/TU for Strange/Fist so if for some reason you are about to be hit with a power/goon CD you can normally make a match to allow Daken to absorb the hit and his strikes work nicely with Fist's attack tile. Fist is there for his attack tile that constantly wears down the enemy plus his purple power that adds black tiles for match 5 potential or hits hard once you get 12 Black. Strange can stun if needed but mostly he's there for his yellow.

When your facing non-goons then I suggest swapping in Cage for Strange since his protect tile will have more value than Strange's yellow. Plus he has that Yellow nuke and can finish a fight (last enemy) with all the Black that Fist generates.

I'd avoid Thanos unless you team him with Daken/Patch because he'll kill Strange in short order so he'll always be needing health packs.

Your 3* PVP defense is not worth worrying about. Your gonna get hit by 4 & 5* teams (or even higher level 3* teams) once you pass a certain point threshold regardless of which 3* you use. Just worry about offense in 3* land in PvP

KGB

P.S. I wouldn't worry much about your 4* teams until you get there. It will take a while to get through 3* land and by then the best 4* teams may have changed with new releases + character buffs/nerfs. Just concentrate on getting the top 5 4* from the December rankings along with Peggy/Carol/Medusa from the newest releases.

Honestly, in the 3-star and 4-star tiers there is so much diversity that there are no 'best teams'. It all depends on the opponent (regardless of PvP or PvE). Its less about strength and more about strategy. When boosted characters come into play the 'best' team is going to rotate. For this reason you want to champ them all; this is especially true of the 3-star tier.

Not much to add here, but I would not recommend using Thanos and Dr. Strange together on the 3* tier.  Dr. Strange works best when he can hide behind a 4* or fellow 3* character, and Thanos in PvE is going to decimate half the health of your Dr. Strange every time you down an opponent.

The other advice I'd give is don't worry about defense in PvP.  Red Hulk, Peggy, and IM40 aren't going to scare anyone away.  I personally believe Peggy is a little overrated on defense unless the AI lucks into cascades.  She's easy to build around to take down.  People will find ways to exploit your defense - you're better off building to win quick matches and using shields, and this is coming from someone who dislikes PvP.

Unsmashable Tim said:

It's not about scaring people with Peggy, rulk and IM40 for me. It's about winning matches quickly. Don't really care about how I finish. I only care about progression rewards 

My post wasn't directed at you; it was intended for the OP.  No one really mentioned the idea of focusing on defense, which most veteran players know is a losing game.  You might win a few matches with a Peggy/Rulk/IM40 team as one example, but that's going to be RNG in the AI's favor when it comes to cascades.

That was my whole point: Don't bother with setting up a "defense team" - you're going to lose on defense more often than you win.  If you want placement, you have to use shields.

As previously mentioned, there are so many characters and so many different activities that there are no "best teams".  That said, here are my favorites:

"Sucker Punch" - 4* Star-Lord + IM40 + 3* Strange.
This is my go-to goon killer. If the node has 2-3 goons, I almost always use this team. Strange's passive yellow inflicts counter-punch damage every time the enemy fires a power. SL's passive yellow creates a countdown tile that reduces the cost of other powers and increases the damage of his Red sucker punch. SL's red can easily hit for 4-5k for a measly 6 red, or go even higher if helped. IM40s yellow powers SL's red nuke and Strange's blue stun, which itself also increases the damage of SL's sucker punch. A successful IM40 recharge can often allow you to one-shot 3 opponents in a row for ~5k each.
Yellow Red Blue Purple.

"Magnetic Storm" - cMagneto + Loki + Mohawk.
The big nukes are Magneto's blue (5k+) and to a lesser extent his red (1500-3k). The goal is to create cascades w the multiple scramble & destruction powers - Loki's Purple & Mohawk's green and Mag's red & Mohawk's yellow.  Hold Mag's red until you have Loki's purple or Mohawk's green charged, then fire Mag's red followed by the scramble powers. It can be a little slow to start, but once it gets rolling it's powerful. And it covers all 6 colors. Hit w Mag's blue whenever possible. It is common that once the cascades get rolling they continue to fuel power after power to hit and scramble and hit and scramble. A weakness is its reliance on cMag to do most of the big damage. If he's taken out, your fall back is Mohawk's black which can do ~1200 every turn.
Blue Red Purple Green Black Yellow.

"Team Cap" - Captain America + Grey Widow + Hulk
This was my first 3* team, so I'm nostalgic. It is a little slow, but solid.  Cap's red is a solid nuke. Widow's purple feeds her big green gun AOE that does 4K+ to the enemy team. That's the big punch of this deck. Hulk tanks and helps generate green by absorbing damage. Cap's blue stunner helps w crowd control and his blue & red both help get rid of enemy tiles.
Red Purple Green Blue

For PVE I strongly recommend Dr Strange, Iron Fist and whoever you have who can deal the quickest strike or best health to take the hits. Dr Strange alone can take out most goons (except Sentry Fighters) by himself quickly.

For PVP I think Kamala Khan, Luke Cage, Iron Man are must have's. Also Thanos, Iron Fist and Dr Strange, but they have issues- Thanos costs you lots of health packs and Strange and Fist have short life spans. Since the AI plays the characters poorly, a good passive helps on defense, especially one that heals the rest of the team. Personally, with my rooster, I tend to avoid those that have at least 2 of those characters. Magneto is also a pain in the behind once he puts his protect titles up. Kamala Khan is who I avoid most. Those with better roosters will eat you anyway.

I can really only offer a PvE side of the equation analysis since I haven't played PvP seriously for a long time.

For PvE 3* usefulness you want the following: IM40(best battery in the game), Strange(passive against goons), Fist (all-around awesome), Switch (purple battery), Thanos (quick kill easy nodes), Hawkguy (all around good and blue/purple generation), Cage (defense and good damage), Blade (three great abilities)

Additional second tier 3* which can be helpful are: Hood (AP steal), Loki (Patch combo), Patch (Loki combo and regeneration), BSGW (Charlie's Angels team with Prof X and Switch), Cap (nice 3* board control option with IM40 pair), Kamala (good all around), Black Panther (good all around), Magneto (good all around), Bullseye (wave nodes), Deadpool (Whales, Whales, Whales), Quicksilver(great tile manipulation black against certain boss battles), Thor (good damage), Cyclops (good damage and red battery)

For 4* PvE: pretty much everything listed above in byc post, although I actually find StarLord to be one of the best for PvE purposes (probably not as big for PvP).  I use the team of StarLord, IM40 ,and 4Thor very effectively for example in many PvEs for certain nodes 

I tried a 3 star team with Spiderman,  falcon, and Magneto. Great defense! Or u can sub Magneto for human torch at 5/3/5 if you want to every color!