I've survived two 6 challenge runs before, both multiple years ago. Now I'm trying to get a million point run and most runs I can't make it out of the sewers. I've even died on the first floor multiple times (usually from a flaming or projectile champion.)
I've mostly tried with Cleric, Rogue, and most recently Huntress (which feels the best so far.) Everything just feels bad. I can't engage enemies at distance because of Into Darkness, I can't ambush them one by one because of Swarm Intelligence, I can't wait and try again later because I'm always starving from On Diet. I get that Supernewb recommends engaging at distance whenever possible and that kind of helps, but enemies close the gap too fast to reliably kill them before they reach me. I'm trying to do trick shots but I don't see opportunities often and I'm bad at them. So far that's the only thing I can think of that I could potentially improve.
If I survive long enough to get a decent weapon or even just reach an alchemy pot, things seem to ease up, but early game I have basically no resources that could be used as a margin for error.
Btw, do you need to ascend a 7C for a million points?