I can’t really comment on all of them, but I’ve got half your 4*s champed and can give my experience with them:
Antman is good for wave nodes and pairs well with characters who give your opponents special tiles or against spam-happy enemies. Though if you pair him with Switch and Fal-Cap you can get punch happy. At 270 and 5 covers, both versions of Grow do 10k unboosted. Granted you’re paying 18 AP for 10k damage, which isn’t the best, but it’s 10k with optional attack tile flooding or special tile stealing.
Opinion: Stronger than you’d expect, less than you’d hope.
Jean: Solid all arounder, if a bit squishy now. You’re going to want to champ her evnetually, since she counters so many things. Though her colors match up to Iceman’s so now might not be the time for her and I’ve found she works better with other 4s than with 3s, since you’re going to want someone to tank for her.
Opinion: Better than most.
Lady Thor: Used to be part of the 4* meta back when both her and X-Force Wolvie were broken. Kinda fell off the map for a little while after they both got nerfed and better 4*s came out. Absolutely killer after the Ironman 40 boost though. Outside of bosses there aren’t many teams who can stop these two on the play. Though she’s not as beast when she’s defending.
Opinion: Stellar transitional character. Highly recommend.
Wolvie X-Force: I still find myself using him, C-Mags, and Loki for PvE and the first few nodes PvP, though it’s been a long time since he’s been top-tier. He’s got some crazy board shake up, but that’s about it. His black can still easily one-shot a ton of characters, even unboosted with the right board; but therein lays the problem -with the right board-. I’m in the minority in saying he’s still worth champing at some point, but he’s far from top priority.
Opinion: Alright, you’ve got better options though.
Venom: Question: Do you find high-level 2* Bullseyes annoying? Because that’s pretty much all Venom is really going to deal with. His green is nothing special, but his yellow packs a punch. At 5 covers it’ll hit about as hard as HB’s red at 9AP. However unlike Repulsor Punch, Lethal Protector doesn’t benefit from excess AP nor is it fueled by Venom’s other abilities.
Opinion: I don’t regret champing him, but I can’t recommend it either.
Kingpin: Just pulled him up to 270 and haven’t champed him yet, so I’ve only used him at 3/5/5. At this build he’s either an OML battery or AP denial that floods the board with countdown tiles. I’ve paired him with 5black Hood and Sam Willson in PvE, and it’s like I’m playing a goon squad. I’ve heard Pin’s black at 5 does bonkers damage for its cost and makes him quite the beatstick when paired with Switch.
Opinion: Solid character. Important for the 4-5 transition but also viable during the 3-4
Buster: One-time king of PvP and still top tier contender. However he only really shines at 5/5/3. Amazing damage output, good health, but not terribly engaging to play as.
Opinion: Super strong but kinda dull.