Devil May Cry 5 Special Edition

The best place I found is on Mission 13 right after the divinity statue. The section after it you can easily farm Red Orbs if you equip Faust and Gunslinger then use his B attack and follow up detonation. After you kill everything, you can restart the checkpoint and if you have Faust upgraded you'll get 500,000 Red Orbs in a few restarts. After you have enough orbs and Faust fully upgraded you can spam its Meteor move that cost 45,000 Red Orbs per use at max level. To do the Meteor you need Gunslinger at level 4, then to use the skill you need to press Forward, Hold RB+B.

Credit for this solution goes to PiledriverX and WilliamRSPOA for the same achievement on the Xbox One version of the game.