His habit of picking his nose is quite off-putting.
Tending to disconcert or repel: “The trappings of upper-class life are off-putting and sterile”
If you describe a quality or feature of something as off-putting, you mean that it makes you dislike that thing or not want to get involved with it. However, many customers found the smell of this product distinctly off-putting. if someone's behaviour or the appearance of something is off-putting, you do not like it or you think it is unattractive
tending to repel; "The trappings of upper-class life are off-putting and sterile"- Elizabeth Hess causing annoyance or repugnance; "an off-putting remark