Rengar

Here is an example, a rough draft if you will, of a champion that could not possibly be crammed into a 5 level PrC:

Rengar
The Pridestalker

A full base class, based on the barbarian

d12 HD
skills 4 + int per level, make sure he has Stealth on the list
Full BAB
Barbarian save bonuses

Level 1

Ferocity: Certain class abilities grant a stacking amount of Fury to Rengar, who can contain a maximum of five fury.  Fury points remain attributed to Rengar until spent on Ferocious Maneuvers, which are advanced versions of three of Rengars abilities.  As soon as Rengar gains five fury, he may, as a free action, perform a single Furious Maneuver at the cost of two of that ability's uses per day.    This ability is to represent the silent rage of a predator, the perfect state of focus.  All distractions from the goal are easily delt with, curtly at best and viciously decisive at worst.  Some sort of competence bonus to rolls, all of them.  The timing of the ability is a free action in order to be scary.  To go from normal Rengar to Total Fury Mode Ultra Rage in the beat of a heart needs to be shocking. 

Bolas: Rengar can throw heavy corded bolas to entangle enemies to slow their escape.  He never runs out of these, he must excrete them constantly, maybe something about his carnivorous diet.  The ranged attack is handled through a throwing method and uses his Str mod to attack with and deal damage with.  The bolas only do 1d3 damage and add half of his str mod.  The target is entangled if struck until they break free (as a standard action) with a Str check or escape artist check vs. DC 10 + half Rengar's Rengar level + his Str mod.  The only problem is that he can only excrete so many of these things per day, something equal to say his Con mod.  Grants 1 fury per use.  These should also be cuttable with small Slashing weapons. 

Furious Maneuver Chuck: The bolas do something.  Something amazing.  Like full damage and the freedom DC is increased by Rengar's levels in Rengar.

Level 2

Roar: As a swift action, Rengar roars like a liger, basically my favorite animal, in order to bolster his defenses through determination and courage.  He gains 1/~ DR and resist cold, elec, fire, and acid 2 until the start of his next turn.  The bonuses increase by 1 DR and 2 Resist for every three Rengar levels that Rengar obtains after level 2 (a total of 7~ DR and 14 resist at level 20).  This ability can be used a number of times per day equal to Rengar's Con modifier.  Each use grants one fury.  Not many uses and short duration should keep the nice buff in check.

Furious Maneuver Roar: Gain HP equal to 25% of Rengar's max hit point total.

Level 3

Savagery: Add extra damage to an attack equal to <  > as a free action.  This ability can be used a number of times per day equal to Rengar's Str modifier.  Each use grants one fury.

Furious Maneuver Savage:  Rengar can use his Ferocity to enact a free primary attack at full BAB and with extra flat damage equal to his levels in Rengar.  This attack can be used at any time.  It can only be used once per Ferocity, pointless to say possibly.  If can be used only on people within range.  This could theoretically allow him to make an unseen predator charge attack from the brush, follow up with a standard action attack (could be vital strike), and then make a free attack using Furious Maneuver Savage.  I think that's awesome as long as there is a rule about Unseen Predator not stacking with any pounce like effect.  Rengar can take pounce effects on his normal charges made as a full round action or otherwise, but not with Unseen Predator.

Level 4

Trophy Collection: As Rengar travels, he ties the souls of his prey into his own via ritualized trophy making.  Using his neck slot, Rengar can begin to build a trophy necklace to signify his dominance.  Each trophy he adds to his necklace must be a reminder of the battles he has won, these items must be physical and be able to weather his adventures, usually a bone.  Each trophy he adds to his necklace gives him a bonus to...

Level 5

Upgrage to bolas:  Bolas now do 1d4 damage.  Can be thrown 10 more feet.  Can be used Con mod + 2 times per day.

Level 6

Upgrade to Roar: Roar deals damage to foes adjacent to Rengar in the amount of his Con Mod.  They get a Will save  to negate the damage, as they refuse to be cowed by his display of lionmanliness.  The DC is 10 + half his Rengar levels + his Con mod.

Level 7

Upgrade to Savagery: Can be used more times a day.  Grants attack speed?

Level 8

Ultimate: Instantly hide, as per Hide in Plain sight rules, for up to 3 rounds with a +20 badass scary fucker bonus. Gain two fury from the next ability used instead of just one.   Ultimate can be used once a day.

Level 9

Trophy Collection:  Uh, the bonus gets better.

Level 10

Upgrade to Bolas: now do 1d6 damage plus his full str.

Level 11

Upgrade to Roar: the damage goes up to 1d6 + con mod. Range is 10'.  Can be used more times per day.

Level 12

Unseen Predator:  Rengar can make a charge attack as a move action as long as he exits full concealment, full cover, invisibility, stealth (as part of the attack) in order to reach his target.  He must expose himself suddenly, like a furry flasher, he comes at you without warning.  He receives a bonus to his stealth checks equal to half his level.  Can only leap his normal movement speed not double as part of this maneuver. 

Level 13

Upgrade to Savagery: Can be used significantly more times per day.

Level 14

Trophy Collection:

Level 15

Upgrade to Bolas: more range. immediate action in response to someone distancing themselves from him. Can be used more times per day.

Level 16

Upgrade to Roar: damage goes up to 2d6 + con mod.  DC goes up by Str mod as well.

Level 17

Upgrade to Savagery:

Level 18

Upgrade to Ultimate:  Gain movement speed.  While Rengar has five unspent fury in his 'pool' he benefits from...something....

Level 19

Trophy Collection:

Level 20

Upgrade to Unseen Predator:  He now adds his full Rengar levels to all of his stealth checks.  And cannot be revealed by any magical means....  Otherwise, Rengar can charge up to twice his movement speed in this manner now.

Uses per day should kinda reflect the cooldown timers on Rengar in LoL. Duh