how to beat otto with 4 weapons:wrench dual lacerators acid detonator and electro rocket. first atack otto w/ lacerators and rockets. if you run out of ammo while he on the ground attack with your wrench then break the crates to get more ammo. on the 2nd part of the otto battle attack with acid detonators since they can hurt even though he still flying.
note: i did this in challenge mode so i had the hyperborean armor which has 90% defense.
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