pulcher

Pulcher, pulchra, pulchrum is a first and second declension adjective that drops the e of the stem everywhere except the masculine nominative singular. The comparative and superlative are irregular in shape but regular in behaviour: pulchrior, pulcherrimus, like all adjectives whose masculine ends in -er.

Two things to watch. The h is a piece of learned spelling, added because Romans thought the word looked Greek; the corpus is full of the older and honest pulcra, pulcris, and the medieval scribes go back and forth without meaning anything by it. And pulcher is broader than "pretty": applied to a deed, a death or a cause it means noble or honourable, which is why Cicero can call a thing pulchrum without anyone picturing it.