To make a long story short, my world has a variety of individuals of varying talents, and along with that, malevolent monsters of the large and dangerous variety, who these people are often employed to defeat (Superheroes, to make a long story short).
One individual has been gifted with super strength. Instead of beating monsters to death with various melee weapons like many who share a similar power do, he has taken a far more unique, and less suicidal approach: Carrying the biggest gun possible to blow these monsters apart.
This man is roughly twenty-five times stronger than an adult male on average, capable of reaching up to fifty times in times of desperation. He is rather large, roughly 7ft and 190kg. He lacks any superpowered way to anchor himself to the ground (and would prefer to not carry some sort of pitons or stabilising equipment which could do so), and is only a small amount tougher than an average human(Hence his reluctance to face monsters head on), meaning any gun wherein firing can produce forces sufficient to physically damage a human body will do so, albeit to a slightly lesser extent than a non-super (For the sake of the question, we'll assume that his super strength means that he won't damage his muscles, bones or joints by carrying these heavy weapons).
He would also prefer a weapon which he can feasibly use, as while he may technically be capable of lifting a certain weapon, its sheer size makes it impractical to aim or move. He will largely be using it as a hip/shoulder fired weapon.
Taking into account features such as recoil, power-to-weight, reloading, and the sheer size of the weapon in comparison to the human body, what is the largest, most powerful weapon which he could practically carry around and use? The technological level is identical to that of real life; that is, if it exists in real life, its fair game. He is also a government entity, so no restrictions on what exactly he can use (For the sake of the question he has access to guns belonging to every country.)
Note: For the sake of the question, weapons defined as "Guns", that is, propellant-based weapons which fire a solid projectile directly at the target, (Anything from a .22 pistol to a tanks cannon) would be preferred over, say, mortars or missile systems.
Bonus round: What is the most practical gun for an individual with super strength to use?