What is an adjective for argument?

There isn't one single perfect adjective for "argument" because it depends on the specific type of argument you want to describe. Here are some options, depending on the context:

For a heated, emotional argument:

* Fiery

* Contentious

* Volatile

* Fractious

* Bitter

* Rancorous

* Explosive

For a logical, reasoned argument:

* Persuasive

* Compelling

* Convincing

* Logical

* Rational

* Cogent

For an argument that is unfair or unreasonable:

* Unfair

* Unjust

* Prejudiced

* Biased

* One-sided

* Invalid

* Flawed

For an argument that is prolonged or drawn-out:

* Protracted

* Lingering

* Endless

* Unending

* Tedious

Ultimately, the best adjective to use will depend on the specific nuance you want to convey.