___ scoring the highest marks in the class, Rohit failed to impress his teacher.

Despite and in spite are similar in meaning but despite will be used here because in spite is used with of.
Though হলো একটি conjunction যেটি clause এর পূর্বে বসে, despite একটি preposition যেটি noun এর পূর্বে বসে। So, Even though is incorrect.
With respect to means regards to or reference to which is incorrect for the sentence.

সঠিক বাক্য: Despite scoring the highest marks in the class, Rohit failed to impress his teacher.