Gradually / Eventually / Sooner or later / At some point / In the end / …end up…

Gradually means that something happens slowly and is not completed immediately. (Can be future tense or past tense.)

• Athena studied English every day for two years. Gradually, she began to speak more fluently.
  
  
• After I broke my leg, I had surgery. Then I began rehabilitation. Gradually, I was able to walk again.
  
  

Eventually / Sooner or later / At some point are similar to “gradually.” These words mean that something takes a long time to be completed.

• The criminal must go to jail for his crime. Eventually, he will get out and return to society.
  
  
• You should stop playing video games so much. Sooner or later, they’re going to make you dumb.
  
  
• Students have too much pressure these days. At some point, they might just snap and go crazy!
  
  
• You can’t just be lazy your whole life. Eventually, you have to get a job and be responsible.

In the end / …end up… is slightly different. This is used to describe what happened in the end. (“…ended up…” should be followed by either an adjective or verb+ing.)

• Don was addicted to gambling. Eventually, he lost all his money. In the end, his wife left him and he was sad and alone. (He ended up sad and alone.)
  
  
• I made the minimum payment on my credit card every month. Gradually, my balance went down. In the end, I paid off my debt, but it took me 50 years! (I ended up paying off my debt.)
  
  
• You shouldn’t be so irresponsible. In the end, you’ll regret it. (You’ll end up regretting it.)