I am not adverse to travel
I am adverse to war.
The verb is "will write"-- we use the helping verb "will" to show that the action (in this case, "write") occurs in the future tense.
I believe you just did so.
matched
The "Y" in you should not be capitalized and while it takes only a noun and a verb to make a sentence - which "I write you" has - it isn't a correct sentence because the tense of the verb is incorrect. "I will write you" would be a correct sentence with the correct verb tense. You could begin a sentence, albeit it sounds a bit odd, with the words "I write you" as in "I write you this letter today in an attempt to appeal to your empathetic side", however "I write you" is not a correct sentence alone.
A verb is the action in the sentance. I will feel the pain in the morning.
"Was writing" is a helping verb (to be) and an action verb (to write). The words "was writing" functions as a verb in a sentence.
I secured the gate.
Here is a sentence with adverse in it.
The verb in the sentence is "written," which is the past participle form of the verb "write."
In this kind of sentence, "how" is usually considered an adverb, modifying the verb infinitive "to write".
You can't write a sentence that is not a sentence, it is either a sentence or it is not. You can write a sentence that doesn't look like a sentence. For example, "Stop!"; although one word, it is a complete sentence. The subject 'you' is implied, the verb is 'stop', which makes it a complete sentence.