The last patch of 2017 is Patch 7.24B, and it isn't even a full patch.
Unlike the typical patches which usually contain new features such as a new game mode, skin, or champion, this patch was solely made to balance the game to prepare it for Season 8, which is to start on January 9th. The goals of patches in the current preseason have been to buff champions that have been struggling to perform in the current meta without the new runes, and of course to tone down the champions that have become too strong.
1. Sorcery Nerfs
Sorcery is arguably the best rune path so far. First, Summon Aery completely dominated the meta because of the damage it could provide, and after its nerf the last patch Arcane Comet has taken its place. Riot is lowering the effectiveness of the entire path in the hope of balancing the abusers of this patch. You now receive 12 AD or 20 AP adaptively, lowered from 15 AD or 25 AP. If you take Inspiration and Sorcery, it is being lowered to 13 AD/22 AP from 16 AD/27 AP. This should be a huge nerf to champions like Varus and Miss Fortune, as it will drastically affect their laning phase.
2. Ezreal, Rammus, Miss Fortune, and Teemo Nerfs
These four champions have been having outstanding performance ever since preseason hit. Although Ezreal was nerfed in the last patch, it wasn't quite enough to bring him back down. His nerf will lower his attack speed growth per level from 2.8% to 1.5%, quite a significant change the later that the game lasts. Rammus' attack speed is also being nerfed this patch. He will no longer start the game with 15% bonus attack speed which should hurt his camp clearing and early game pressure quite a bit. With the sorcery nerfs, with which MF and Teemo rely upon quite a bit, they will feel much weaker in the laning phase. On top of this, the cooldown on MF's E, Make It Rain, is being increased quite significantly early. Because of Arcane Comet's synergy with her E, she was able to get free poke damage. Having her E up less often will surely lower her effectiveness in the laning phase. Teemo's health and AD per level are both being decreased, which means he will be less powerful both early and later on.
3. Top Laners are getting Buffed
Top lane fighters such as Renekton are feeling a bit weak because they have now lost their armor and MR runes. They can no longer build damage items early because poke champions like Jayce will tear through them. The buffs won't increase their tankiness, but rather focuses on increasing their damage so they can fight better in lane. Renekton and Kled's base AD and AD per level are being increased. Kled's E is receiving more damage, along with Yasuo's Q. Yasuo's cast range on his ultimate is being increased as well as his MR per level. Tiamat and Titanic Hydra, very popular tank items, are also being buffed by 5 AD each.
4. Mid Laners are getting Nerfed
Katarina, Corki, and Azir have all been in a surprisingly good spot at the moment. Katarina's E, Shunpo's base damage is being decreased. Corki's AD, both base, and per level are being nerfed and his Q, Phosphorus Bomb's base damage is being lowered. Azir's soldiers will do less damage at level 7, and then again at level 13. Zoe's Q-Q-R combo is being refined to allow for leeway in timing, and the cast range indicator of her Q, Paddle Star will be clearer when she casts her ultimate to make it easier to use.
5. Lethality Changes
The bonus Lethality on Lethality items that were added to compensate for the Lethality that would be lost to the new runes is being reverted. Each Lethality item, Serrated Dirk, Duskblade, Youmou's Ghostblade, and Edge of Night now have 2 less Lethality each. Although a minor adjustment, it will certainly have a notable feeling on assassins or any other champion that stacks Lethality.
With individual nerfs to Miss Fortune, a nerf to her rune path, and nerfs to her favorite items, she is definitely getting hit the hardest this patch. Due to this, she will most likely lose her spot at the top of the ADC tier list and may even fall out of the current meta. This is the last patch until January, the official start of the next season. Between now and then, Riot will most likely use micro patches and/or hotfixes to solve any remaining issues before pro play begins.