"It's not clear in the original whether it means condition or character or ability..." (kafentzou's comment, see posts under translation)
If it means condition:follow kafetzou's translation
If it means character/ability to do smt : "Είμαι χειÏότεÏος/χειÏότεÏη (masc./fem.) από ÏŒ,τι λες, αλλά καλÏτεÏος/καλÏτεÏη(masc./fem.) από ÏŒ,τι νομίζεις"
"I am worse"--> "more bad (like "bad in doing smt"" or "in a more bad condition"? "χειÏότεÏα" and "καλÏτεÏα" are adverbs (worse condition/shape etc.)
It's not clear in the original whether it means condition or character or ability - sorry! I used the adverb because that way I didn't have to choose a gender, either. You can feel free to reject the translation if you want to.