[Auraleus]

I think this is, but beter safe then sorry:

SPOILER!!!!
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The only really "forced" dragon fight is towards the end of the game when you have to beat up the green(?) dragon in elf town

All other dragon encounters are by subquest or passive:

-Red dragon fight in windspear hills
-Shadow dragon fight (which is avoidable from having an item in you inv) in temple ruins
-Silver dragon quest, she gives you a quest in the underdark and will only attack you if you go swinging your sword at her head first

I think thats all of them