Celebi

The time-traveling Pokemon Celebi is here through Special Research and unfortunately, it isn't a big performer. Its stats are similar to Mew, but lacks the moveset versatility. Magic Leaf helpped it in terms of its Grass Type damage, making it a potentially viable option, but its damage is still definitely on the low side of the spectrum. 

Best PvE Offensive Moveset

• Confusion is the fast move of choice, and outperforms other options against neutral opponents.
• Magical Leaf is viable when Grass-type moves would be Super Effective.
• Charge Beam is useless. 
• Psychic is Celebi's strongest Charge Move, sporting good power, STAB, and synergy with Confusion.
• Leaf Storm is a second STAB option, and pairs well with Magical Leaf to fulfill a Grass-type role. 
• Seed Bomb is a downgrade. 
• Dazzling Gleam doesn't offer much to Celebi.
• Hyper Beam is a joke of a charge move.

Confusion is one of the better Fast Moves in the game, sporting 4 DPT (Damage Per Turn) and 3 EPT (Energy Per Turn). It hits hard and charges moves at a fair rate. Magical Leaf is now an option following the Johto Tour in February 2022, and offers above average damage output and energy generation, along with Grass-type coverage. 

Seed Bomb is recommended for its lesser energy cost, and with STAB it deals respectable Grass-type damage. Psychic might be a bit redundant due to the high damage output of Confusion, but it benefits from STAB and costs a moderate amount of energy. Leaf Storm can be chosen for its very high burst of damage, but can be risky to use due to its self-debuff. Dazzling Gleam provides Fairy-type coverage which can be useful against Dark-type opponents, but its high energy cost discourages its use.