幸运 （XING4 YUN4）

It depends on using different phrase as '幸运xing4yun4', '走运zou2yun4' and '运气yun4qi4'.

侥幸的 as well

If you mean a one-character tatoo, I would suggest ‘顺’, although all the translations above given by my colleagues are correct. ‘顺’is a good word with many different meanings. Basically it means going on smoothly without changing direction, or following the stream naturally and obediently. It also widely used to discribe the situation where everything being done successfully and smoothly. It is one of the popular character used to discribe good luch. You may know that some Chinese people like the number 'six' because it means ‘顺’, that is, good luck. One of Chinese rebelling peasant leader even named his dynasty as ‘大顺’( ‘大’means great), although it lasted only a little more than one hundred days.