Hulk is strongest one there is. Alex strikes me as a a Venom knock off, without the sensivity to heat and sound. I'm pretty sure Hulk would get mad enough to eventually hit him harder than he's ever been before. That would probably be escape velocity strength. If he didn't die due to the extreme cold of outer space, the lack of oxygen, or the lack of air pressure, the burn up of reentry would probably finish him off.