to make the quality of something worse

• enhance
• improve
• degrade

• progress

moving forward using new or modern ideals

• stagnant
• progressive
• regressive
• traditional

able to be changed back to an earlier state

• irreversible
• permanent
• unchangeable
• reversible

easily hurt or harmed

• vulnerable
• invincible
• indestructible
• resilient

to return to an earlier, usually worse state or condition

• regress
• improve
• evolve
• progress

happening in a slow way over a long period of time

• sudden
• rapid
• abrupt
• gradual