How can Rengar be effective if he fails his early game snowball?

Solution 1:

In the situations in which rengar has low stack of tooths or simply cannot burst he should be built similar to other tanky dps (Mostly damage sponge and sustain with enough damage to hurt against low defense targets).

Build Suggestion: In the case where you're falling off you should shoot for the heart of gold quickly for your GP5. Depending on your lane opponent or where your damage is coming from you will want to grab a warden's mail early or get your merc treads. Grab a phage for a bit more health and damage plus an additional slow to your bolo.

Your end build should be Frozen mallet, Randuins Omen, Merc Treads and Last Whisper as your core items. This plus your necklace should provide a lot of damage, CC to hamper a retreating target and CC to hamper the entire team. Depending on if you have a lot of damage coming in from magic or not you may want to pick up either a wits end, maw of modius, Guardians Angel, Force of nature or Bandshee Veil.

Team Fight Strategy: Your job is simple in this case. Stand amongst your team, wait for an initiate (Don't get caught by AoE) and as soon as the fight starts, Ult and land on top of their AD carry. Pop your randuins as soon as you do and go all out on that AD carry. Your reduced damage shouldn't matter since he's gonna be squishy, if he's stacking armor your last whisper should cut it down, if he's not it's still gonna help (If they have more than 30 armor the last whisper does more damage than an unstacked bloodthrister). Your warden's mail will reduce his attack speed for attacking you and the armor should keep you alive.

Your job in every fight is to stick to that AD carry as a damage sponge that can kill him. He will not be able to just ignore you and you take a fair amount of time to die thanks to your debuffs. Add in exhaust for extra CC on him and lock him down from the fight. He will probably kill you, but by doing this you force their team to focus on a damage sponge thats on top of them instead of your carries. They will be bunched together if they focus you, perfect for your AoE CC and the randuins slow prevents them from splitting up outside of flashes.

That would be my strategy in this case. Use different skills at different times depending on the AD carry (Leap on corki a second time if he dashes away or bolo him with ferocity, etc)

Solution 2:

To me, Rengar seems to be by his nature one of those snowball champions. Just like Shaco and AP Yi, if he doesn't pick up a few early kills or get really great farm, he just can't quite pick up the steam he needs to get going.

That said, I think you have two options at that stage.

1. Try to become an off-tank for your team: If you weren't already building in an off-tank manner, start converting over. Definitely pick up your Frozen Mallet as soon as possible, and maybe even go for an "Atmog's" build (Warmog's Armor plus Atma's Impaler) despite the recent nerfs to the latter. The reason this makes sense is that Rengar performs the role very well.

   • Initiation: His ability to initiate or chase down opponents (triggering a team fight or preventing them from fleeing) is extremely good due to his passive leap, his Bola Strike (especially if at maximum Ferocity), and even his ultimate if you want to use it. Often times it is the team who is able to initiate better, when their team is in the favorable position, that wins the team fight -- and often solely for that reason. Thus, even if you are underfed or underleveled, you can still contribute immensely in this way.
   • Soaking Damage: While Rengar may not be the best champion for this, he is certainly not the worst. His self-heal gives him decent sustain, and with that as well as his CC he is able to stay up and about long enough to let the rest of his team do damage. Your death is perfectly acceptable as long as your team comes out on top.

2. Become an assassin: Really, Rengar shines here anyway, but you will essentially have to take this to the next level. You will have to choose your engagements very carefully. Think of yourself as a weaker version of LeBlanc in this scenario; your job is to run in, kill someone quickly if possible, and run back out... wait for your abilities to come off cooldown... and do it again. This is one of the best ways for you to continue to be relevant. You also make an excellent character for "clean up" duty after a team fight as it is very difficult to actually escape a Rengar when he is chasing you (and most players will default to running through jungle brush to get away... which is the last thing they ought to do, and which will assure you the kill).

Of the two, I think the first one has the most chance of being useful, but the second one, while it has greater risk, has greater reward, as it is probably the most effective way to feed your Tooth quickly and become truly relevant in the game again. The choice of which route to go will also obviously be affected by the state of the game and what roles need filling in your team, etc.

Solution 3:

Either build tanky and soak up as much dmg as possible (if your team has a good top lane bruiser/assassin like Irelia) or build Aura items (Zekes, Aegis, even Abysall if your team is double AP and noone else wants/can get it) and try to assassinate low life enemys.

Thats what I usually do, I have a pretty good win/loss ratio. You should always try to figure out if you can snowball or not at the start already. Against jungle Alistar, you wont be able to snowball anywys, you can build aura items!