Tech and Nature Together

A pretty simple Forcefield Generator + Repurpose build. Both Groot's forced interrupt and Forcefield Generator have the same timing, so you get to choose which one to take damage on to lose counters with. The goal being to get your Forcefield Generator as low as possible without getting to 0, that way you get max value before dumping it with Repurpose.

Then for some more Repurpose fuel, a couple of the otherwise lame Plasma Pistol you ideally use two of the charge counters from first for some low damage, maybe to clear tough status cards that can otherwise be annoying before your large hits if your little allies can't deal with them. This way you can get huge stats and multiple readies in one turn. Assuming you have Symbiote Suit on yourself at this point with a Forcefield Generator and a Plasma Pistol, two Repurposes will get you to 8 THW or 9 ATK, and that's after you already got to first do a basic THW or ATK for 2 or 3, then a basic THW or ATK for 5 or 6. Now you just use C.I.T.T. for another ready, and he's got his own built in ready with Lashing Vines, Flora and Fauna is another ready if you draw it, and then dominate the board for either giant damage or giant thwarting based on what you need at the time. Just keep in mind with Repurpose that you have to choose either THW or ATK, so you're going all in on one or the other once you start boosting your stats.

Ideally the Forcefield Generators help you keep your growth counters high so your events can hit for 10ish damage or thwart pretty consistently, your allies pick up slack where you need it, and can chump block when needed for big hits, or thwart enough to let you flip and get more counters. It might depend on player count and scenario, but when you have a 10 thwart event like "I am Groot" it can be good to let threat build a bit on the main scheme so flipping down to alter ego every other round is probably fine in most cases. If you can pull off a "We Are Groot" when you have a few allies on the board, you'll have chump blockers for days.

I've had pretty good success with this deck, and find it quite fun to play as well. I hope you enjoy it too! No more Groot at the bottom of tier lists!