Channeling increases most weapon's melee damage by +50%. Corrupt Charge increases Channeling's damage based off this value, thus at max rank it increases Channeled melee damage to +100%.
This can be combined with Killing Blow for +220% Channeling damage, or a total damage increase of +160% while Channeling.
A -40% decrease in Channeling Efficiency translates to an additional 2 Energy per hit while channeling. Without Channeling Efficiency mods, using Corrupt Charge increases Channeling cost to 7 Energy per hit.