"Drastic changes" refers to significant or extreme alterations or modifications in something. It suggests a noticeable shift or transformation that is substantial and often unexpected. Full definition
The people you see who make drastic changes in short time are literally about.1 % of the people who attempt to lose weight. (coachcalorie.com)
Start the habit of healthy eating now, so you don't need to make drastic changes in years to come due to health issues. (fitbodyhq.com)
During the years in which drastic changes of structure were being made, those involved largely took the content of the gospel for granted. (religion-online.org)