unsympathisch
unlikeable
A person who makes an unpleasant or off-putting impression on others and does not inspire sympathy.
Ich fand den Verkäufer sehr arrogant und unsympathisch.
I found the salesperson very arrogant and unlikeable.

unpleasant / unlikeable
Loading your saved state.
unlikeable
A person who makes an unpleasant or off-putting impression on others and does not inspire sympathy.
Ich fand den Verkäufer sehr arrogant und unsympathisch.
I found the salesperson very arrogant and unlikeable.

Careful: 'unsympathisch' means 'not likeable, unpleasant, off-putting'. It is not the same as the English 'unsympathetic', which means lacking compassion or understanding.
Ich kann ihn nicht leiden, er ist mir einfach unsympathisch.
I can't stand him; I just find him unlikeable.
The word is the direct opposite of 'sympathisch' (likeable). The prefix 'un-' reverses the meaning and expresses a negative personal feeling.
Sein Lächeln wirkte auf mich irgendwie unsympathisch.
His smile seemed somehow unlikeable to me.
Because 'unsympathisch' describes a personal feeling, it is very often used with a dative pronoun that names the person who has this feeling. The structure is: 'Jemand ist mir/dir/ihm unsympathisch' (Someone seems unlikeable to me/you/him).
Seine arrogante Art ist mir total unsympathisch.
I find his arrogant manner completely unlikeable.
nice
'nett' and 'unsympathisch' both describe the impression a person makes on others, but they mean the opposite. A 'nett' person seems friendly and pleasant. An 'unsympathisch' person seems unpleasant, or you do not particularly like them. 'unsympathisch' does not necessarily mean that someone acts impolitely; it is more about the personal impression. 'nett', by contrast, is a positive impression of the person and the way they deal with others.

Der Mann im Bus war ruhig, aber er wirkte auf mich unsympathisch.
The man on the bus was quiet, but he seemed unlikeable to me.
Im neuen Büro ist meine Kollegin sehr nett zu mir.
In the new office, my colleague is very nice to me.