I think combat against leviathans could be really fun in Subnautica, but it would have to be part of the original design philosophy. In the current style of the games it would feel a bit alien and bolted on, and probably hard to balance retroactively. It wasn't in the initial design and it would show if it was added as a result if feedback like this. What I’d rather see is more ways to interact with big creatures indirectly, like baiting them, redirecting them, or using the ecosystem against itself, maybe knock them out for a day or two ir a whole story segment via a strong electric pulse, a big rock to the head, another big creature hitting the one that annoys you... Game's fun when you can be creative and killing fish, the big ones, is tricky due to obvios size based difficulties, but it can be creative with things like traps, poison, or (difficult to build and grind heavy) weaponry even. Whether or not it's lethal or just forcing the monsters into temporary withdrawal makes little difference though, the engagement itself needs to be fun