on the other hand, while, whereas, however, nevertheless, still / yet, in spite of / despite 

On the one hand, Internet is a great tool in education but, on the other hand, it has many disadvantages.
Tow is very smart while hai brother is not.
She had made her homework, however, she didn't get a good mark.
He is very wealthy, yet very happy.
It was raining. Despite this, they went out