Misirlou

All these fancy X-23 decks trying to do something other than Aggression.
Well, I say it's time to take things to X-23's fast paced core and pump that attack up and up and up!

That's our basic goal of the deck, boost our attack to the point that Wolverine would be proud how we snikt our bubs.

Does she look like a bitch?

We have to following ways to boost X-23's attack
Claw Mastery
Combat Training
Combat Specialist
Symbiote Suit
2x Adrenaline Rush
X-23's Claws

That last one we'll likely only use after we've attacked at least once, but that's fine. If we have Grim Resolve out, it will likely just be an attack boost and we use Grim Resolve to ready instead.
Adrenaline Rush works amazingly well with X-23, it sits around waiting for you to pull the trigger at the right time and start blasting your enemies into oblivion.
The rest are all upgrades that will be boost our attack long before we land the finishing blow.

Honey Bunny

Without a doubt, Honey Badger is central to any X-23 deck and ours is no different.
Attack Training on Honey Badger is amazing, if only to make it easier to keep the little sister around before we see our Regenerative Longevity.

The other reason is that Game Time with Honey Badger leads to additional X-23 attacks.
The more we can make use of her boosted attack, the better!

Sisterly Bond leads to amazing damage turns too and at worst, it allows Honey Badger to thwart for 3.

The Wallet that says Bad Motherfucker

To get to our awesome high attack power, we need to get a good amount of upgrades down for X-23 and as mentioned before, Honey Badger and her copy of Attack Training are kinda key to commit absolute murder.

Because of that, we kind of want to draw as many cards as possible. Not to mention, the faster we cycle through our deck, the more often we can use Sisterly Bond too. Because of this, we have a mini-minion slaying subtheme with Angela and Looking for Trouble leading to Hall of Heroes counters that we can use when we go and heal to draw a bunch of cards. It also makes it so that we have stuff to attack most of the time.
Combined with IPAC and Weapon X, there's a lot of card draw.

As for our one very special upgrade, Combat Specialist, we can only get through Specialized Training. In 2+ hero games, our other heroes might be decent to good at thwarting, but X-23's Animal Instinct makes her surprisingly potent at thwarting and she can contribute significantly to the goal of completing Specialized Training. Once that is in play, our first basic attack will draw us a card too!

The Royale with Cheese

In the end game, if we have all of the above out, we'll be attacking for 6 (7 or 8 depending on if we saved our Adrenaline Rushes), then using X-23's Claws to ready and boost it up to 8 (or 9 or 10) and attack again. That's when we'll attack with Honey Badger to ready again, who will hopefully be equipped with some Attack Training for at least another 2 damage. But hey, we got that Sisterly Bond and maybe we'll boost Honey Badger by another 8 attack too. All this means that on the lowest end, we'd have 23 damage (6+8+1+8) on the high end, we'd sit at 40 damage (8+10+12+10), all coming from having upgrades in play and playing only a Sisterly Bond.

This brings us to Quick Strike, which functions as a pseudo-ready. As we don't care about actually performing basic attacks, but just making use of her snikt-potential, it effectively works as another basic attack and often hitting an enemy for 5+ damage on top of what we were already doing. At the end game? Like I showed above, it can easily do 8 to 10 damage.
And obviously, Game Time will add a ton of damage too, or potentially a thwart with Animal Instinct. You have a lot of options, but by the time you have all the upgrades out, you are likely just straight up ending the game.

Consider my ass retired

So this is the deck slimmed down to 40 cards. Honestly, it has quite a bit of draw power and the original version is 42 cards and I think it won't hurt to go up to that amount either because it barely harms the consistency and you flip often enough to heal back up and make use of Hall of Heroes that you draw a lot of extra cards anyway.

So additional cards to consider:

Battle Fury - Amazing to ready after killing a minion and do more stuff. A single copy is definitely handy, but unless the scenario is really minion heavy, you don't need to kill multiple ones in the same turn usually.

Wolverine - Papa Logan is a sweet ally and with the low curve and high draw power, you do technically have the resources needed to easily play him at some point. The problem is you don't need the attack he provides and a free thwart for 1 a turn is not amazingly interesting.

Psylocke - She's amazing and the confuse helps you flip down, especially in solo. By all means, include her over Wolverine, she'll provide value.

Adrenaline Rush #3 - I feel 2 is more than enough, but a third copy would allow for potential even higher ceiling of how much snikt you deliver to the bubs. You really don't need more, but might be be a consideration to hit higher attack numbers more often

Sunfire - He's great and we're alright with throwing a Game Time or Adrenaline Rush his way for his ability. Another X-Men to throw Attack Training on of course, but we really want to save those for Honey Badger.

Brute Force - Yes, it boosts our attack. The problem is that it falls off and we prefer having our upgrades stick around for more consistent damage over the course of the game. So you could include it, but it didn't feel right for the deck

Jarnbjorn - We do enough damage already, we don't need MORE damage

Godslayer - Only lasts for the attack, not interesting, Don't do it.

"Now I'm Mad" - Cool design, but despite all the self damage, you often heal a lot and won't consistently sit at 4 or less HP. Especially with Adamantium Lacing, Endurance and Symbiote Suit