10 Characteristcs of   a good tester is :

1) Critical Thinker
2) Should be diplomatic enough to handle Developers, in 
order to maintain Team spirit.
3) Domain Knowledge should be most important.
4) Well versed in communation and should be expressive .
5) knowledge of Language platform would be an added 
advantage.
6) Must be aware of QMS ( Quality Managemant system)
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thats all what hits in my mind.