Charizard will now be OU. It has been solidly around for several years now, firstly seeing play on Mixed Offenses and now also getting used with more and more moveset options in TSS. It is quite similar to Moltres and they're both good in their own regards, with each having upsides and downsides. It also commonly sees play in high level ADV events such as Callous Invitationals or SPL. Finally, it is frequently used at an OU level usage on the high ladder (1500+).
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Charizard is an underrated* threat in ADV OU with its powerful Fire Blast threatening a large part of the metagame and its great speed tier allowing it to outspeed or tie with most of OU. Its Fire type coverage alone is excellent at threatening the OHKO on many metagame staples like Metagross, Skarmory, Forretress, Magneton, Jirachi, Celebi, Heracross, Breloom and Venusaur, but it is also equipped with great coverage moves like Focus Punch to hit Tyranitar and Hidden Power Grass to hit Swampert.
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*- Charizard is currently in the C2 Rank in the ADV OU Viability Rankings, with Moltres being higher than it for many reasons, the biggest one being that Moltres sports a higher base Special Attack than Charizard, and not being limited to two good sets (Mixed and Sunny Day in Charizard's case).
Overall, Charizard catapulted to OU in ADV as it saw extremely high usage on the ladder, is comparable to Moltres as an offensive Fire-type Pokémon with immunity to Spikes, and is preferred on TSS (Toxic, Spikes, Sandstorm) teams than Moltres.
Hope it helped.
