How do I counter Sustain?
I've been playing top a lot lately, and I have realized that the majority of "meta" champions at top has some incredible sustain built into them. Despite that, they also have decent damage and tank stats to utilize while their sustain is keeping them alive.
So, my question is how do I exactly fight an enemy with high regeneration? I can't win trades, and as a top laner, my burst isn't exactly spectacular either.
I would like to know a way to fight sustain without sustain myself, a lot of champions I've seen are boarder line toxic to gameplay as they turn the laning phrase to one giant battle of attrition.
Edit: Thanks to all those who responded. Many has asked me to clarify which champions I usually pick for top, and they are Irelia and Riven. To show my current difficulties combating sustain characters, here is a match I played yesterday as Irelia:
Against Lee Sin (minimal life steal.) http://matchhistory.na.leagueoflegends.com/en/#match-details/NA1/1593357430/219216356 and against Dr. Mundo (Heal to full ult) http://matchhistory.na.leagueoflegends.com/en/#match-details/NA1/1594666413/219216356
It seems no matter what I do, I cannot even force Mundo to pop his ult unless I use mine as well. Even then, I often fail to kill him and I then no longer have the potential damage to burst him down again until my Ult is off CD.
+
with more 
(and also grievous wounds it)
might help (but you'll lose the early game stats you'd gain from a doran's item).
....
are viable end game items.