Im.going to say someone like sion, renekton, vlad, chogath or lissandra. You need someone who is tanky, has waveclear, and does enough damage to squishies that they can't be ignored. The list I gave fits those, along with having enough cc to help (except vlad, he is pure damage + waveclear). With the champs I listed, you should be playing under turret, and your main goal is to clear waves as fast as possible. This will force them to tower dive to get you.
Ince they do that, cc whoever is tanking, and go.for a squishy if they are close enough you can get them when.you are parallel to the turret.
Rinse and repeat, and if.they took 50% of.your hp, back off slowly to the next turret while still wave clearing.
If.you are looking to slow down a 5 man group without turrets aiding you, your best bet is honestly to kill their ads with an assassin. Leblanc is probably your best bet simply because of how easily she can get in and then out.
Another iption is talon. He has waveclear and can assassinate and get out of the situation calls for it.