Nouns often end: -ment, -ion, -ness, -ity.
People nouns often end: -er, -or, -ist, -ian.
Adjectives often end: -able, -ible, -ive, -al, -ic, -ed, -ing.
Some verbs end: -ise, -ate, -en.
Adverbs often end: -ly.
Is the new word negative? If so, you may need a prefix, e.g. un- (unhappy), im- (impolite), in- (inexperienced), dis- (dishonest), etc.