Although not a native speaker, I think the answers above are confusing, so here goes: 偏偏 Has three main meanings 1) When something "違反常情“, when something someone else wouldn't expect you to do 冬天雖冷，我偏偏就想吃冰淇淋 按理說靠近沙漠的地方不會下雨，可是卻偏偏下了雨 2) When the thing that happens is exactly what you don't want (this is by far the most common usage) 難得的假期，偏偏遇上颱風 禮拜天我去找他時，偏偏他不再家 3) To express "only", same as 單單 or 唯獨 大家都搭公車，偏偏你就是不走路 別人都來你，偏偏你沒有來 Laurence

偏偏 = on purpose, purposefully to be contrary. All other meanings are just variations of this main meaning. You can see from all the above given examples. 叫你不要做, 你偏偏要做, I told you not to do it, you purposely wants to do it.

It seems unreasonable that...

e.g. 大家都来了，偏偏你没来，为什么？

In another word, you should have come with us, but you haven't.

她脾气可好了，偏偏找了个脾气这么差的家伙。

Actually, you have to know its meaning and the feelings/ emotional colouring behind it. Meaning is really simple: 正 vs 偏 (a couple of antonym) 正 a state which is not only upright but also positive, centering, symmetry，and main. Such as main religion vs pagan religions. 一张贴得很正的poster means not crooked, askew. So the opposite of 正 is 偏 For examples: a ball 射偏了 = 没中 = miss 走偏了 : perhaps you want to go back to your home, but you arrive at your neighbor's house. Besides: 偏偏 is emphasis. Thus, 偏偏 has a kind of meaning: unexpectedly. 偏偏喜欢你: a girl said: "unexpectedly, i fell into love with you idiot! " but 偏偏的 emotional colouring may is implying a meaning opposite to what it said = i love you very much!