Is there any way for Friendlies to kill Hired Guns while last resort is attached?

How is the Rancor healing and damaging the Hired Guns?

You can't attack or cleave damage onto your own figures under normal situations (See your Rules Reference Guide).

It was campaign anyway. I was referring to the feed ability.

Pretty much the only way to kill your own stuff is by using abilities like Grenadier and Bossk's Indiscriminate Fire which damage a whole area regardless of friend or foe. Or mission effects like the Dianoga's attacks.

I have done it before with the Royal Guard Champion. Throw a Grenade, do some damage and also kill my 1 health trooper. That triggered RGC's Executor ability and he got to move up and smack something.

Good trade for a 1 health trooper that was about to die anyway.
It's even better if you can get a parting shot and/or last resort explosion out of it.

It is a trick you can use but it's pretty rare. Hired Guns don't usually survive long enough to set up a fancy combo like that.