I am (in general) a fan of steel types. Up until the recent changes in Pokemon cards, the only way to provide metal energy was to use special energies (which were rare) or to use rainbow energies (which had health or HP drawbacks). Now, metal energies are in basic form. Steelix Prime is one of the best steel types to have in a deck.
Steelix plays the role of a tank perfectly. It has 140 HP, which isn't sky high, but it is a decent amount. It has one resistance and one weakness, which is to be expected. He is an all purpose, heavy hitter. He has 2 moves:
1) Energy Stream, which does 30 damage and let's you search for an energy card in your discard pile.
2) Gaia Crush, which does a straight 100 HP and allows you to destroy a stadium in play.
Strategies and game play:
Using his Energy Stream is a good way to provide Gaia Crush with the massive amounts of energy needed to use that move. Once you can use Gaia Crush, use it as much as possible.
Combos with other cards:
Use the special Metal energies as much as you can, because supplying Gaia Crush with 5 Special Metal Energies will lower any damage done to Steelix Prime by 50 points.
Ways to counteract it:
Hit him hard and fast, because Special Metal Energies will keep you at bay. Fire types are his weakness, so take that into account.
Gaia Crush does a devastating 100 damage, enough to wipe some stage 2 cards off of the board. Since he is a steel type, he gets the Special Metal Energy bonus (-10 damage done to Steelix by an opponent for every special Metal Energy)
The 2x fire type weakness is not surprising, but Gaia Crush needs 5 energies to move, which can take eons. (5 energies is 1/12 of your deck).
None that I know of.
Artwork and aesthetics:
I like Steelix Prime's artwork, it does a good job of showing the meaning of "Crush".
For high HP, strong attacks, but a 2x weakness, and a move that requires 5 energies, I give it a 8.