I don't want to do low chaos and get the bad ending again (this is my second time running through the game).
I got high chaos on the first level. Will that make me have a bad ending?
31 Answer
No, getting a high Chaos rating on the first mission alone will not make you get the high chaos ending (which I assume is what you meant by "bad"). It seems like you need to consistently get high Chaos ratings the entire game to receive the "bad ending."
For instance, a user in this thread states that he got a high Chaos rating on the second level, but didn't get the bad ending:
I got a high chaos rate on the second mission and killed around 15 on the others missions together. I still got the good ending
According to the wiki, in order to receive the "bad ending", you must have killed at least 50% of all encountered Dunwall citizens:
3If Corvo's total kills exceed 50% of the population seen in Dishonored, Dunwall is irrevocably thrown into chaos, and the high chaos ending is depicted.