retrogress

verb retrogress

• degenerate — If you say that someone or something degenerates, you mean that they become worse in some way, for example weaker, lower in quality, or more dangerous.
• deteriorate — If something deteriorates, it becomes worse in some way.
• die off — a sudden, natural perishing of large numbers of a species, population, or community.
• fall away — to drop or descend under the force of gravity, as to a lower place through loss or lack of support.
• fall off the wagon — (Idiomatic) To cease or fail at a regimen of self-improvement or reform; to lapse back into an old habit or addiction.