Discussion Points
Mega Altaria S -> A+
Mimikyu A -> A+
Mew A- -> A
Nihilego B+ -> B
Slowbro B+ -> B
Mega Houndoom B -> B+
Hoopa C- -> UR
Alolan Marowak C- -> UR

Possibilities
Latias S -> A+
Registeel C- -> UR