Last week, a number of major Pokemon Trading Card Game (TCG) tournaments took place around the world.
In the West, we’ve had the NAIC (North America International Championships). Meanwhile, in the east, there was the Japan Championships. In both of these tournaments, we saw an awful lot of Marnie’s Grimmsnarl ex making it to the top percentile.
Marnie’s Grimmsnarl ex:

Marnie’s Grimmsnarl ex is a Stage-2 Pokemon that was recently introduced with the Destined Rivals expansion. Offering extremely fast energy acceleration for any of Marnie’s Pokemon Grimmsnarl is a fantastic threat that can even hit benched Pokemon.
It might not be the most powerful Pokemon in a toe-to-toe fight, but its capacity for speed and damage spread can put it in an early advantageous position.
Deck List Analysis:
The two deck lists below are from some of the top percentile placers from the NAIC (Piper Lepine) [Left] and the Japan Championships (Naoya Honda) [Right].

While there are some differences between these decklists, it's worth noting how noticeably slim the energy pools are in both decks. Marnie’s Grimmsnarl ex facilitates one of the fastest energy acceleration strategies in the Pokemon TCG, so not much is needed. Even top-performing peers would run about 9-12 energy cards depending on the deck.
The moment Marnie’s Grimmsarl ex hits the field, that’s an automatic +5 to your hand, even if they’re all basic energy cards.

Second, both decks are running Froslass and Munkidori from Twilight Masquerade. The two work synergistically with Marnie’s Grimmsnarl ex to help fling damage to softer targets on the opponent’s bench. Having multiple copies just compounds this effect further.
Munkidori especially benefits from Grimmsnarl’s energy acceleration. Marnie’s Grimmsnarl only needs 2 out of the 5 Dark-type energy it searches out to go online.
Even if a player has a second Grimmsnarl being built on the bench in case of an emergency, that still leaves leftover energy for Munkidori to operate its ability with.

As for the Trainer cards, outside of staple cards that you’d normally find, like Secret Box or Boss’s Orders, we can see that both players have opted to use both Technical Machine: Evolution and Technical Machine: Devolution.
The former helps build multiple copies of Marnie’s Grimmsnarl ex without relying too much on the use of other searchers that have an inherent cost like Ultra Ball.
Devolution comes in as a way to counter a wide board of robust evolved bodies once damage counters have stacked high enough via the trifecta of Marnie’s Grimmsnarl, Froslass, and Munkidori hitting the bench.

Alongside these, both players have a small roster of Stadium cards featuring Spikemuth Gym and Artazon.
Both count as consistency tools for players to rush into whatever missing piece their board requires for the match. Additionally, they both counter any enemy Stadiums that could prove too hazardous, like Jamming Tower.
Tournament Match-ups:
Gardevoir ex

Marnie’s Grimmsnarl ex plays very well into this match-up despite Gardevoir ex’s status as one of the strongest tournament competitors in the Pokemon TCG currently.
Most Pokemon in a Gardevoir ex-centered deck are Psychic-type; Munkidori, Jellicent ex, Lillie's Clefairy ex, etc. So Marnie’s Grimmsnarl ex is essentially hitting a lethal 360 damage for just two Darkness-type energy.
Even if you didn’t account for the added damage that Grimmsnarl, Froslass, and Munkidori were all doing together, Psychic-types just fold to Grimmsnarl’s initial burst.
Dragapult ex

This one is a more balanced match-up. Dragapult ex, for the same amount of energy, does a lot more damage than Marnie’s Grimmsnarl ex.
There’s also the fact that most Dragapult decks today are running a backup unit in the form of Charizard ex or Bloodmoon Ursaluna ex. Both of which are good catch-up mechanics, should the Grimmsnarl player get too much of an early lead.
In a match-up against Marnie’s Grimmsnarl ex, these two decks would be roughly even in damage output and consistency. It would be up to player skill and a little luck, as you can still lose to a bricked hand, to determine the winner of the match.
Raging Bolt ex

A match-up with a Raging Bolt ex can be very disadvantageous for Marnie’s Grimmsnarl.
One, Raging Bolt can actually just one-shot Grimmsnarl ex with sheer brute strength. Two, there’s usually a Teal Mask Ogerpon ex and the occasional Iron Leaves ex in the deck list.
Not only does Teal Mask Ogerpon ex have the type advantage to bridge a lethal threshold quite fast, but its Tera quality allows it to ignore the damage done by Grimmsnarl.
This gives Teal Mask Ogerpon a little more longevity to build up and swing in for a sweep.
Iron Leaves ex can easily come in to tag-out for a finishing blow when at match point, just because of the type advantage it possesses.
Some Final Thoughts
Marnie’s Grimmsnarl ex has easily rocketed up the meta standings. It can compete with the rest of the current leaderboard in all, if not most, facets that make a competitively viable deck: energy acceleration, consistency, and damage output.
The only thing to consider is the potential disadvantageous match-ups. Marnie’s Grimmsnarl ex does have its weaknesses with Grass-type or if the opponent has a one-shot function like Raging Bolt ex, but that’s par the course in TCGs.
If anything, player skill and luck are still a factor even in the grandest stages of this hobby.