Multiple Opponents
Tier: 2
Activation: Passive
Ranked: No
Your character adds one Boost to his Brawl and Melee combat checks when engaged with multiple opponents. This includes single groups of multiple minions.

Does this mean that, if the person was facing of against a group of minions and a rival and attacked the rival, would the bonus apply? Or would it apply when he attacked the minion groups? Or would it apply against the rival and the minions?

I ruled that it worked only when attacking the minions as the rival was only one person and he was not fighting multiple opponents but I am looking to see what other people thought.

It doesn't sat "attacking," just "engaged with."

As long as the character is engaged with multiple "opponents," they get a boost on brawl and melee combat checks.

Yes, if they're engaged with a 1 minion group and 1 rival, they would benefit. If they were engaged with 2 rivals they would benefit. If they were engaged with a single minion and one rival they would benefit. If they were engaged with a minion group of 5 minions, they would benefit.

If they were engaged with one rival they would not benefit. If they were engaged with a single minion, they would not benefit.

The main reason for that phrase "includes single groups of multiple minions" is to represent they even get this boost when fighting one minion group. What is key is there being more than one enemy generally.