What prefix could be added to this root word form a that matches the definition plus conservative very conservative?

The prefix that could be added to the root word "form" to create a word meaning "plus conservative, very conservative" is ultra-.

Ultraconservative is the word that fits this definition.

Here's why:

* Ultra- is a prefix meaning "extremely" or "beyond"

* Conservative refers to a political or social philosophy that emphasizes tradition and established values.

Therefore, ultraconservative means "extremely conservative" or "beyond conservative."