In your opinion what are the best and worst reworks?
----------> This is more focused on the rework concept as opposed to balance on release <---------
We've seen a fair share of reworks that have needed some fine tuning after release, but have/could be brought in line with some numbers adjustments. So again, this is not based on initial balance. I'll start.
#BEST:
: In my opinion the best rework Riot has ever done. Visually and thematically spot on. Old Sion was a goofy model with a bizarre, clunky kit. They reworked him into what felt to match his character perfectly. Sion - The Undead Juggernaut. His kit and appearance really gives him that feel. Charging his team into battle while still feeling fair to play against. Lots of room for counterplay while still feeling rewarding for pulling off. Hats off to you Riot. Well done.
: Might not be the most popular of reworks, but his new kit feels so much more engaging than his old one. You actually feel like you are doing something as opposed to being a super linear, point-and-click CC bot with a targeted heal. His old ult was mostly hidden power so it felt kind of useless. The new Taric is more dynamic and has more things to do in fights. You actually feel like you are helping and his ult is amazing when used properly. All in all he's a much more fun champ to play
#WORST:
: Not entirely sure what they were trying to do with him. His kit is full of gimmicks and what-the-fuck moments. Absolute balancing nightmare that they had to gutter for a long time because they couldn't deal with it. A melee ADC replacement? That doesnt even make sense because one of the major roles of an ADC is to siege objectives like towers and inhibs from a relatively safe distance. People have finally found a way to play him, but he is 100% completely reliant on Rylai's to function. You can't have a champion that functions around a single item because when that item changes they change with it. And whats with that pet Dragon? I wonder how much of his kit he had to sacrifice for that gimmick.
: This shouldn't be a surprise to anyone. They just can't get him right after multiple reworks. Its a meme at this point lol. What do I have to say that everyone doesnt know already? Riot continually messing up his reworks then reworking him again to try to fix it. His current iteration is almost unplayable on a team of strangers thrown together. He's been relegated to the "Competitive-only" category and been left to rot along with Azir and Kalista.
So how about you?



and
more engaging for everyone involved and undoubtedly the golden standard of juggernauts. strong self-synergy in his own kit means he isn't horribly item reliant and his passive rewards him for staying in fights. very good rework and imo much better than most of the full VGUs we've gotten with far less work involved
and 
I personally play Garen and I thought he plenty fun really, but they didn't create a less binary or give him options to enter the fight with. I chose him because i liked most of the reworks but Garen's falls short because of what it really accomplished.
to compensate for that weakness despite it being a significant early game investment.
is really strong, I admit that, he works in many comps, he can control the map with his crystals and is very good at isolating that one important target and dragging him to his doom. But while this is a really strong niche to be placed in for Skarner, he feels very boring to play which loses it's appeal all together.