If you have to redo the whole level including easy parts that are lengthy then that's just bad design. I shouldn't have to go through a gazillion easy enemies to get to the part that's actually hard. That just fakes difficulty by making you go forever to get to the hard part.

Git gud scrub

I do not agree.

I think Destiny is a good example of a game that does it pretty well (though not perfectly). When you die in an easy section, you respond in pretty much the same place. The harder sections (called darkness zones) take you back to the beginning of the zone. Most of the time this is a moderate, but not terrible setback. In all cases, you retain any loot that you picked up.

There needs to be some consequence to dying, otherwise there wouldn't be as much of a feeling of accomplishment for progressing through a game.

Agreed.  The frustration felt when you die without a recent save has actually caused me to quit a game, and more than once.  I should have remembered to save, of course.  But, it just doesn't happen sometimes.