Mew

Mew is a very unique and versatile Pokemon, as it has access to many valuable moves. This, coupled with a solid Speed tier and good bulk, allows Mew to support its team in a number of ways. However, while its bulk is good, its Psychic typing leaves it walled heavily by Incineroar and Mega Metagross, as well as causing a weakness to U-turn, a prevalent move. It can carry offensive options like Ice Beam as well to help take on certain threats, but it can't provide much offense outside of preparing for specific matchups. It's important to remember that while Mew may not be the best option for filling one specific role, its ability to perform multiple roles in one slot is what makes it useful. On the same token, if the selected moveset isn't particularly helpful in a certain matchup, Mew can be quite the momentum suck.