One universal antiviral to rule them all?

Maybe, maybe not. Antibiotic resistance develops because antibiotics are only somewhat deadly to bacteria, so natural selection can occur and bacteria develop resistance over time. There are some antibiotic/bacteria combinations where this doesn't happen, because the respective antibiotic is so deadly to that special kind of bacteria, that no survivors can pass on their slightly increased resistance.

And bacteria self-replicate, whereas a virus needs to infect a cell and be reproduced by that cell. Some antiviral mechanisms attack the reproduction proteins that the human cells use, which the virus cannot do without. And the human cells don't have reproductive pressure to replicate viruses, quite the contrary.

Is a fair analogy, antibiotics kill, whereas antivirals use birth control? So viruses would have to find a way to circumvent the replication inhibitors or potentially find a noval way to replicate.

Some classes of antibiotics use birth control - rather than killing bacteria directly, they inhibit reproduction.

I think the biggest difference is that bacteria can react to a treatment, while viruses don't have the capacity to react. If you've stopped a virus from replicating, it's essentially dead. A bacterium may have defensive measures it can take. It could form an endospore and try to wait things out. If you've stopped it from reproducing, as it ages it might start accumulating free radicals that increase DNA damage, leading to a higher chance of it mutating to resist the antibiotic. Etc.

Antibiotic resistance costs bacteria dearly. The proteins they lose (typically related to cell membrane building) are honed by millions of years of evolution. The resistance mutations end up being inferior, slowing down growth and perhaps other capabilities.

> I think the biggest difference is that bacteria can react to a treatment, while viruses don't have the capacity to react.

Bacteria also swap genes between themselves [0], whereas two viral particles sitting on the same Petri dish are too inert/simple for that. That represents an additional way for adaptive tricks to spread.

https://en.wikipedia.org/wiki/Horizontal_gene_transfer