"I am sadder than you."
Translation:Ben senden daha üzgünüm.
You may omit "daha" in some sentences, if not all, since "-den/-dan" also gives the meaning of "daha". In this sentence, I would use "daha", to make it clearer; but also without it, the sentence still gives the meaning. Some examples:
"O benden (daha) güzel."
"Sen ondan (daha) çalışkansın."