As other people have pointed out here, Vengeance ability happens as part of a reaction. If you want zero room for wiggle in RAW the Tempest domain cleric's lvl 6 works with elemental weapon, polearm master, and the Command (approach) spell.
Okay new approach then because of the "reaction" word in Oath of Vengeance level 7 ability.
Now we go with Tempest Cleric's level 6 ability - whenever you deal lightning damage you knockback 10 feet
Combine with elemental weapon (lightning) cast by yourself (bard 6 on top of cle 6, this is...
With this combo you can target any number of people with command saying "Approach". End your turn within 15 feet of the next one in intiative order
For demonstrations sake, lets say you target 3 people (maybe more with a quickened version as an MC sorcerer, but let's not go down that route...