I like this word, if the definition is correct.
Xấu roughly means bad, and tính means calculate/calculated (like máy tính. So xấu tính basically means a calculated bad.
Is that right? That's really clever.
It's even easier than that, the other meaning of tính is:
disposition (of people); nature; character; temperament.
And that's how „xấu tính“, „nóng tính“ (hot-tempered) and some other words are formed.