Hard To Deal With, Weak Point, Poor At, Not Very Good At, Bad At
noun, な adjective
A "suffering hand" is a little misleading. Think more in terms of the words 苦い (bitter) and 手 (person... remember how that happens sometimes?). Now think of this word like you're bitter about having to work with someone. Why? Because they are extremely hard to deal with.
にがて
The reading is that of 苦い (にがい) plus regular old 手 (て). Remember, this is your bitter person, the person who's "hard to deal with." So, it uses the strange にがい reading.
セロリが苦手です。
I'm not a big fan of celery.
あのアイドル、歌が苦手なのが欠点なんだよな。
The drawback about that idol is that she is not a good singer.
うちの犬がなんでお前にばっかり吠えるかって?正直言って、お前のことが苦手なんだよ。
Why does my dog bark only at you? To be honest, you are not his favorite.