You can use the items from the series called Risk of Rain. Too bad you don't have them, but don't worry. When you defeat an opponent that has some sort of supernatural ability, they have a chance of dropping an item or piece of equipment, and the odds increase the stronger the opponent is in comparison to you. This can be any item from the Risk of Rain series, including, but not limited to: Teddy bears that can completely negate an attack; glasses that give you a chance to double damage; glowing meteorites that everyone will hate you for.
If a duplicate item appears that you already have, you can merge them for a 2-in-1 deal. You can also undo the process and give the item to someone else to use if you desire. The item needs to be on your person to work, but the items have an unnatural ability to seemingly always stick.
With enough items, you might be able to shred an endbringer in a few seconds.