Well, it's pretty easy once you get the hang of it.
Go up in your Ratticator suit. Sneak up on him and attack him like you would do to Jimmy the Neck, etc. 3 robots will fly down. Defeat them all. Alfred will come back. Sneak up on him and attack him like you would do to Jimmy the Neck, etc. 3 robots will come back. Repeat the process one more time. After the 3rd time the 3 robots fly down and you defeat them, Alfred will come back one last time. He will actually be defeated when you attack him like you would do to Jimmy the Neck, etc. Yet, I'm not going to spoil the ending