AoE weapon effects in combination with fragments that produce orbs... AoE ability effects in combo with fragments and armors mods. Ex. There's an arc fragment that produces orbs from any kills when amplified... add to that Reaper, Siphons with a Volt shot weapon... many many orbs, often multiple per kill. There's many different ways to do it...

So mods that generate orbs only generate one. A second copy only makes it give more super energy. In order to generate multiple orbs on a kill it needs to meet 2 or more criteria. Such as a multi kill and a subclass aspect. Supers will generate more than one. The power preservation mod makes them generate more per kill as well. I think that is still a mod. It used to be on helmets.

load up your armor with Orb mods , check you subclass for ones that creates orbs. I used grenade kickstart and melee kickstart and just go crazy used strand, took me 13 hours of strikes. You will get people speed running that will lower how many you get . use the super on big groups. it gets boring after a while but push through.