I seem to have a horrible time against people who have insane combos, or only need one kill to absolutely curbstomp the lane. Are there any champions and vice you could lend to stop this from happening? I have the hardest times with Riven and Akali.
Know their cooldowns, range, damage, dodge skills shots, control minions waves. Theres no particular way of stopping it. Maybe give us a certain champ your having a problem with, and we can suggest advice vs that champ.
My knowledge base on both are pretty low.. Akali is like %100 banned, and rivens are rare/i never top.
Though both are weak to range+cc, and if focused in team fights are blown up. And they dont have the best team fights.
Akali: Destroy her 1-6 ( No excuse to die to her pre-6 ever) - Some counters are annie/lee/mord/garen
Riven: If its her early game your worried about, her aoe normally shoves, so farm under turrent and wait for ganks.
Also im pretty sure GAREN- counters both, maybe pick him up lol. https://www.youtube.com/watch?v=I6uFjuEDk9g
(Also if its ranked, better off banning akali, dont want your team to feed her.(Fizz too)
People who have strong early games (Darius and Renekton both come to mind) will generally have an easier time. Snowballing champions fall off hard if you can keep them from building up in the early game. Harass them out of lane, and if you start having a hard time work with your jungler to set up ganks and force them out of lane that way. Keep vision of your river because chances are the jungler might be prioritizing their lane to get the snowball rolling so he can not worry about top anymore and proceed to gank only mid and bot.
Riven relies on her mobility. Force her to use her dash/shield to close distance and just keep backing away, wait until she's blown her combo, again keep backing away and as her shield falls she'll get your minions aggroed to her. If she uses her Q to get to you, let her as you keep backing off. She loses much of her burst if she's forced to waste Qs. If you haven't seen her use her stun in the last five seconds, assume it's up and keep from getting that close. Once she's level six, if you haven't seen her use her ult in the last 30 seconds, assume it's up. Again, work with your jungler to harass her out of lane or to prevent her from snowballing you too easily. If she gets to the point where she's cocky enough to start turret diving, make her work for it. When she starts going in on you, hide on the opposite side of your turret so she has to blow as many little hops and dashes as possible to get to you and has nothing left to get back out of range of turret. Lead her on a merry goosechase around your turret as she continually takes shots. The moment a Riven starts pushing up the lane, if your jungler is nearby ping for help. Bring it to their attention that she's pushing up. Even if she's got River warded it'll still make her back off, letting you get some farm under turret. Beating a Riven is all about dodging what you can of her kit, even if that means walking through her to make her mistakenly carry herself too far forwards with a Q and miss, and abusing her cooldowns because she's next to worthless without them unless she's already super fed.
Akali? Build MR. That's literally the best advice I can give you. After she blows her burst on you, she's pretty much helpless while she hides in her smoke. Take someone with strong AoE abilities who also has a shield, or is inherently tanky. Renekton or Rumble could both worth. Survive her initial burst, try and CC her, and if she sits and hides in her smoke to keep you from hitting her stand in the middle of it and use AoE abilities. Renekton's Q will still hit her. If you're Rumble, hit your flamethrower and laugh. Better yet, considering she won't go in until level 6 in most cases which means you should either be at or near it, if you have your ult available lay it across her smoke at an angle where she has to walk through it to get out for as long as possible. Use the slow to keep on her, keep her slowed with harpoons, save your shield for when she's most likely to have more stacks of Shadow Essence, or for when her Q is about to come off cooldown.
if they are the snowbally ones without a doubt they will be aggressive and try to kill you
rather than facing them, risk dying and letting them snowball I go passive, trying to avoid their engages
or idk play Quinn ;l shes always been my "safe" pick cuz I can poke frequently and safely and disengage whenever they try to engage and reengage immediately after while they cant do anything
Play Quinn with an avarice blade for free gold and just keep disengaging every time they try to start the ball rolling. with an avarice blade you can safely lose a cs here and there to stay safe.
Akali relies on her stealth circle to hide while her cooldowns reset, and building up marks on you so she can combo you down. Having a tankier character with an MR buy first back is good, also swap to a Sweeper and buy the Pink ward to put near the middle of the lane. If you can maul her after she pops her circle you can win usually, especially if you pull back out of range every time she puts a mark on you.
I've had good luck fighting her with Swain and Cho'Gath, if you are looking for something like that. Both of them can hurt her if she comes close for her lvl 6 combo, and they also CS pretty safely so she can't get you when you are low.
If a champion was able to easily burst 150% of your health, the game would be annoying and become a race to who push R first. Because of that gameplay restriction all assasins can only burst you exaclty at best. (this is before you give them 5 kills duh..).
And because of that overarching rule, a simple 
immune you to 1 hit-ko. just itemize so your laner can't nuke you. It's shouldn't be so hard to understand...
