In general, yes, you can absolutely put strong enough line on that will let you haul a fish straight out of the water dangling from it. It you fish for small fish (perch, bluegill, etc.), that's basically what you do every time. They are small enough that even the lightest line will still hold them.

The challenge, though, is that the stronger the line is, the more visible it is to the fish, and the less finesse you have when fishing with it. More visible line can spook fish and get you fewer bites. And a thicker, stiffer line can make it harder for you to work the lure in a realistic way that entices fish to bite.

So you're always making the trade-off where lighter line means more bites but a greater risk of not landing the fish if it breaks the line. Stronger lines mean fewer bites but if you get a hookset, you can probably land the fish.

There are other complications too: fish aren't the only thing in the water. Stronger line can help you not lose lures if it gets tangled on branches or other obstructions.

On the other hand, lighter line is more fun to fish with. You feel what the fish is doing much more clearly and the fight is more interactive. Catching a small fish using a big stiff fishing rod with heavy line feels like listening to music with earplugs in. You lose a lot of the experience.

Also, there are different kinds of line: monofilament, fluorocarbon, braid. And you don't have to use the same kind of line for the whole length. Sometimes it makes sense to have a leader (a short section of line at the end) that's lighter or heavier than your main line.

One of the delights of fishing is that it's an endless problem-solving exercise in gear optimization.

This is also why some guys like to pike fish on ultralight gear.

'Course, then they'll probably snag all the time.

It has some downsides, though: it's a little stiffer and thus harder to tie knots in. It's less resistant to abrasion (being dragged over rocks, etc.). But it mostly disappears in water.

That's my understanding as well. That said, I hate fluoro line, especially on spinning reels, as the extra stiffness gives it a tendency to want to come off the spool already. Add in any extra "weird" factor like a badly timed gust of wind when casting, and you wind up with a big tangled birds-nest of line wrapped all around your reel. :-(

OTOH, there's a another "superline" formulation out there, that is made of the same material as braided line, but it's fused instead of braided together. The Berkley Fireline Crystal version claims to be nearly invisible in water (similar to fluoro) while still having the strength, suppleness, etc. of braid. I've been using it for a while and have been pretty happy with it.

That Fireline looks interesting.

That line already exists today. Fishing line is measured in breaking strength, so a 10 lb. line should reliably be able to withstand 10 pounds of force before it snaps. (In practice, it's less because knots are always the weak point. Also, it's a gamble as to whether a manufacturer accurately measures their line's strength.)

Gravity exerts a force in the same unit, so if you want a line that will let you lift a 50 pound fish out of the water, 50 pound line will do it. Maybe 60 or 70 to give yourself a margin of error and account for the fish's thrashing. The line will be somewhat thicker than lighter-weight line, but not enormously so.

So the literal answer to your question is just: Go to the store and buy a line whose test weight is somewhat above the weight of the fish and you'll able to muscle it onto the boat without having to tire the fish out first. Your local fishing store will have line heavy enough to do that for almost all fish.

The obvious follow-up question, then, is, if you can just go to the store and buy that, why don't anglers do so? And my comment is mostly an answer to that.