Unassertive and Unsure

Unassertive adjective - Inclined to timidity or lack of self-confidence.

Unsure and unassertive are semantically related in hesitant topic. In some cases you can use "Unsure" instead an adjective "Unassertive", when it comes to topics like passive.

Unsure adjective - Not feeling sure about the truth, wisdom, or trustworthiness of someone or something.

Unassertive and unsure are semantically related in unconfident topic. Sometimes you can use "Unassertive" instead an adjective "Unsure".