To whom it may concern, I made a small list listing the multi-classes ranked optimized and above:
Barbarian - Fighter
Bard - Cleric, Fighter, Paladin, Sorcerer, Paladin
Cleric - Ranger
Druid - Cleric
Fighter - Barbarian, Rogue
Monk - Cleric, Fighter, Ranger, Rogue
Paladin - Bard, Sorcerer, Warlock
Ranger - Cleric, Fighter, Rogue
Rogue - Fighter, Ranger
Sorcerer - Paladin, Warlock
Warlock - Fighter, Paladin, Sorcerer
Wizard - Cleric, Fighter