How Do You Spell HADDEST SENSATION?
Pronunciation: [hˈadəst sɛnsˈe͡ɪʃən] (IPA) 
The word "haddest sensation" is not a commonly used phrase in English. However, if we break it down phonetically using IPA transcription, we can see that "haddest" is pronounced /ˈhædɪst/ and is the archaic second-person singular form of "have". Meanwhile, "sensation" is pronounced /sɛnˈseɪʃən/ and refers to a physical or emotional feeling. Therefore, the correct spelling of the phrase would be "you have had the sensation" for modern English.
