Deterioration, Getting Worse
noun, verbal noun
A bad change is exactly what it sounds like: deterioration, aka getting worse .
あっか
This is a jukugo word, which usually means on'yomi readings from the kanji. The on'yomi readings of the kanji are あく and か, but here they become あっか, to make the word easier to pronounce. Try and say it out loud to see if you agree.
ストレスのせいで、病気の悪化が早い。
Stress is causing the disease to worsen quickly.
昨日の夜、インフルエンザが一気に悪化した。
Last night, my flu suddenly got worse.
最近この辺りは治安がかなり悪化している。
In recent times, there has been a notable decline in the overall safety of this neighborhood.