An opinion
A thesis statement.
An opinion
A direct demand
If a guy tells you that you are cute or pretty, he is very interested in you.
You can call a hippo who thinks she's sick a 'Sicko Hippo'.
A person who believes they are being harassed could be called a victim or complainant, depending on the context of their situation. It's essential to provide them with the necessary support and resources to address their concerns.
A person who believes in aliens is often referred to as an "alien enthusiast" or someone who is "believes in extraterrestrial life."
Gullible.
You would him/her Gullible.
A creationist.
Religious.
One who believes that everything is predistined -FATALIST