What is wrong about this sentence: Most people do not like taxes; although, people like what taxes pay for.

I believe that the conjunction you used in the sentence is incorrect. Instead of 'although,' you could say 'however,' and the sentence will be correct and actually make sense.

Most people do not like taxes; however, people like what taxes pay for.

"people like what taxes pay for". Take out the first complete sentence "Most people do not like taxes" and "; although.". Once you take those out you should have a complete sentence, but you don't. Adding a word like 'most' in front of 'people' would make the sentence correct.