What's the difference between 済ませる【すませる】 and 終える【おえる】?
I've tried looking at jisho.org, goo.ne.jp, ALC, HiNative and here, but I'm still unsure about the difference between these two words. I think it might be that 済ませる【すませる】 is used for things that are unpleasant to do. Am I right, is the difference something else, or are these words just synonyms?
「おえる」is paired with「おわる」。Somewhat contrived example:
Highschool has ended.
高校がおわった。
I have finished high school.
高校をおえた。
These two sentences are basically the same. Even if you use the active voice "finish", you don't have any control over when your highschool education ends. (Okay, you do have some control but not much.)
So, even though おえる is an active voice, its content is passive.
In contrast,
I have finished work for today.
今日の仕事をすませた。
Here you can finish your work quickly if you work hard. You have a lot of control. You can't finish your high school education as you finish your work for the day. So, すませる is a bit like "dispatch" in this context.
By the way, おわらせる is more similar to すませる than おえる is. In many cases, おわらせる and すませる are interchangeable.
According to the question azimicat posted in the comments, 済ませる【すませる】 most likely really is used for negative/upleasant things.
