Is there a build that can solo kill everything in hell? Perhaps elemental druid with hurricane (cold) and tornado (physical dmg) ? any better ideas?

essentially the chars that can solo hell are:

Assassin
Druid
Necro
Sorc
Barb
Amazon
Paladin

Meteor / Orb Sorceress can do pretty much Everything, Low Gear req.
Good ladder Starter imo

My 50cents

Hammerdin with shako

Summon necro

Pala is OP imo with Zeal. Max ias, some cb, max resist, splash of hit recovery, max block. Holy Shield jacks up their defense really high. As standard with any melee, life leech / life tap. Piece of cake. I like Baranar Star + Guillem's. BStar will kill Phys Immunes (eventually lol but it's usually just ghosts).

Trapsin with good merc gear (maybe throw a wand of lower resist on switch for light imm. tough spots). Mind Blast + DS is just fantastic. Fade is OP.... but necessary.

Summon Necro has ridiculous utility. Iron Maiden vs Duriel. Clay Golem + Holy Freeze Merc with Kelpie Snare + Decrep vs any other boss = the boss just sits there. Confuse is OP. You can practically solo hell naked with a summon Nec. Just Gloams become an issue, so not quite naked for everything.

Sorc needs 3, 4 or 5 piece tal's. Maybe just a wand of LR is enough to help. Really the only thing that makes Sorc worth the time is Teleport which is essential in a ladder reset imo for the easiest time progressing and mfing from scratch in the least amount of time.

Paladin

Trap/kick sin, good for pvm/ubers.

easy solo - get spirit sword, lore helm, insight, all favoring a caster or mana/+skill based character; hammer pali can get spirit shield too, which is free and a ton of stats for start.

If you care about fast, sorc is going to always win with tele - i like to grab some sapphire/ruby in cheap gear for the free stats and then get a spirit and insight on merc, also leaf is basically free for the extra warmth at lvl 19. You can respect to fb/orb or any single element at some point. I like ~6-8 warmth too just to speed things up until you get real gear.

As above said, all classes have hell-viable builds that can self find, but casters are a bit easier in general because of lower gear requirements to do ok damage + attacking at a distance/summons/etc. I'd say in terms of easy mode but not boring after sorc + hammerdin: light trap assassin, psn necro with corpse explosion or summoner slanted necro, with javazon, wind druid, and maybe frenzy barb being most consistently easy to get going at start for each class.

There are tons of low runewords to make most builds okay: https://www.ocf.berkeley.edu/~gkwan/d2/search.html#/runewords

use your imagination really

If you got all day to clear the pits once..