One universal antiviral to rule them all?

Wont viruses just adapt and now we've got worse viruses as a result? Isn't this kind of why doctors don't like to prescribe antibiotics too often, because they become ineffective in the long run.

I'm genuinely asking, I'm a simple software dev not a doctor.

Of course. Given unlimited time, viruses will develop resistance. Resistance = evolution = descent + modification + selection. You can quibble about whether viruses are alive, but they definitely evolve.

But so what? Anti-pathogen drugs are useful in the period during which resistance hasn't become universal, and if and when it comes a problem, we'll have other drugs.

Besides: sometimes you get lucky and the virus goes extinct before it can develop resistance (e.g. smallpox)

That's not really true. Evolution is constrained by physics, so while bacteria can evolve to live in 100C water, they can't evolve to live in molten magma, or the surface of the sun. Similarly, they can evolve to live off of isopropyl alcohol, but they can't evolve resistance to sufficiently concentrated bleach (sodium hypochlorite).

I'm not sure what you consider "sufficiently concentrated" but some existing viruses (which form spores) can already survive a 1% sodium hypochlorite solution cleaning, which is pretty crazy-high. At that point you're risking damage to surfaces/skin. Doesn't seem impossible it could go higher if bleach exposure was consistently selected for.

Surviving in 1% bleach doesn't demonstrate the supremacy of evolution over physical constraints, and it's important to keep the eye on the ball of what this whole point was about. There are circumstances such as the temperature of the Sun, where DNA, or any molecular structure, or even atoms, can't hold together, and so there's no evolutionary pathways that can iterate toward survival. You can't have molecular biology without molecules.

It's an extreme example, but it demonstrates a fundamental constraint that can't be evolved around. Ideally vaccines can find an equivalent in the space of mechanistic interactions that cut off any evolutionary pathway a virus could reach, either exterminating the virus before it has enough time to complete the search, or by genuinely leaving no pathway even with infinite searching.

Contrary to what you may have heard from Jeff Goldblum life does not always find a way.

Yeah, wasn't disagreeing with fundamental premise, just picking on the bleach bit.

My sentence construction was a little ornate but the antecedent was "bacteria", not "viruses and bacteria and anything else you can imagine"