How does Radiation work?
Randy Pitchford confirmed further details about the new element type. The nuclear radiation effect will increase the vulnerability to your enemies that have been affected by it. On top of that, it also has a damage-over-time component. This sounds a lot like the Slag element from Borderlands 2, however, that didn’t have the damage-over-time effect. Randy Pitchford also confirmed that Slag won’t be returning in Borderlands 3. If an enemy dies from radiation, they will explode and the radiation can spread to nearby targets.
What is Slag?
In Borderlands 2, Gearbox Software added Slag to the game. Elemental weapons could harness Slag. Damaging an enemy with it would have a chance to Slag them. Turning your enemy purple which would make them vulnerable to other damage types. So you would should them with a Slag weapon and once they are weak you would switch over to another weapon to deal double damage.
While this was a fun gameplay mechanic in your first playthrough, on the overpowered levels this became a chore. Because enemies have so much health you were forced to slag them or else you would be up against giant bullet sponges.