Like, if I search youtube right now for any game+bad ending. I get results of the "evil ending". (Assuming said game has multiple endings.)
1. this is called selection bias.
1a. Try searching evil ending for the exact same game (one with both an evil and a good route) and you will get the same result.
1b. Try searching for games where instead of "evil vs good" route you have "MC has bad things happen to him vs good things".
the selection bias is twofold. first you are choosing games that have an evil vs good route instead of different scales of victory. (or a game that mixes the two by making you a loser if you are evil and a winner if you are good. such as Dishonered)
second, you are choosing to use search terms that confirm your biases instead of checking search statistics to see which is used more.
2. a better method is to search youtube for just "bad ending" without specifying a specific game. Then look through the results to see which ones are evil, which one are loser, and which one are a combo of "taking the evil route makes you a loser".
I just did and the results are...
First few results are Five Nights at Freddy
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where bad is "you fail to free the trapped souls". You were not evil, just a failure.
Next I see Hollow Knight
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Which has a whole bunch of endings and most seem to be cases of "you failed to get best results". However I am not all that familiar with the game. Can you actually play as evil in that game?
Next is a video about Ghost of Tsushima
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where there is no good or evil route. Instead you have a final choice at the end of the game of killing the big bad (who wants to die) or refusing to kill him on the basis of him having no honor and thus not being worthy of your sword (the ending which the video is referring to as "bad ending").
So, not evil but bad results.
Then a clickbait "list" video "7 bad endings that were unediably cooler".
Games with multiple endings often include a 'bad' ending to make you feel bad about the bad job you did. But you might not even realise that you’re looking at the so-called bad ending because what is happening is undoubtedly cooler than whatever sunshine and rainbows nonsense you get in the canonical conclusion. Consider these supposedly bad endings that were undeniably cooler than the goody-two-shoes alternatives.
So... clearly it is speaking about you doing a "bad job" aka being a failure. rather than being evil.
Next a video about breaking bad...
next a song.
next deathloop.
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this is complicated. you could make a reasonably well made argument that killing your daughter to end the time loop was evil. Even though she is not really dead as you both awaken together on the beach the moment after you do so. Although she hates you now for taking away the time loop from her
and that is the end of the first page. So... as far as I can tell all the examples on the first page of results are where bad = loser.
of course I could engage in selection bias to get whatever result I want by cherry picking games.
for example searching "fable bad ending" and "fable evil ending" gives identical results. And in fable you very much have an Evil route. Comically over the top Evil at that.
or I could go the other route and pick games where there are only "loser" endings and no morality involved. in such games bad will always mean what I said it usually means.
either way it would be selection bias. you need to not specify the game if you want to avoid selection bias.