suspicious

be, feel, look, seem, sound

become, get, grow

The detective grew suspicious when the witness kept changing their story.

remain

make sb

The fact that he never answered his phone made me suspicious about what he was doing.

deeply, extremely, highly, profoundly, very

I was extremely suspicious when my friend suddenly offered to pay for my lunch.

increasingly

a bit, a little, rather, slightly, somewhat

She seemed a bit suspicious when her husband came home unusually late.

immediately, instantly

naturally

She was naturally suspicious of strangers after her bad experience with online scams.

rightly

She was rightly suspicious when her friend suddenly offered to lend her a large sum of money.

about

The manager felt suspicious about the sudden increase in expenses last month.

of

The old man grew suspicious of the stranger who kept asking questions about his house.

be, look, seem, sound

That man's behavior seemed suspicious to the store manager, so she called the police.

consider sth, find sth, regard sth as, treat sth as

The teacher regarded his sudden improvement in test scores as suspicious and decided to investigate further.

highly, very

The man looked very suspicious when he refused to answer any questions about where he had been.

not remotely

The old abandoned house didn't look even remotely suspicious to the new residents at first.

a bit, rather, somewhat

see/hear anything suspicious

If you hear anything suspicious in the night, call for help right away.