Too many variables... From your first run(s), you're very likely to die a good number of times, it's part of the learning process of the game. You do something, it doesn't work, you die. Then you realize how to not die, and you don't die.

As for completing the game... Also too many variables. What is "complete" in an unfinished sandbox? If the question is can you play hardcore once you know what you're doing and kill the current bosses without dying, then yeah probably. (I couldn't, last boss is tough but I'm sure people do it.)

Btw, you can remove those death markers on the map.