The correct spelling of the phrase "haddest passion for" can be explained using the International Phonetic Alphabet (IPA). The first word "haddest" is pronounced as /ˈhædəst/ with the stress on the first syllable. The second word "passion" is pronounced as /ˈpæʃən/ with the stress on the second syllable. The phrase means to have a strong love or desire for something. It is important to use correct spelling and pronunciation to convey the intended meaning in communication.