If one would really want to name the two terms in question, one might say: * überentwickelt for overengineered (not really used) * unterentwickelt for underde

If one would really want to name the two terms in question, one might say: * überentwickelt for overengineered (not really used) * unterentwickelt for underdeveloped (matches the word, even) "Unterentwickelt" is a term we do not use lightly, since it is a word we often used in elementary school to bully some kids, so that has that smell to it. (Usually you also add a howling sound to that word and give yourself a smack on your forehead ;))