No other Juggernaut is so reliant on perfect conditions to deal damage like Illaoi is. Not all need to be met but most of them do. Here are her conditions:
She needs tentacles set up around her prior so that she has damage. If this isnt possible then she loses out on a bit of damage.
She needs to land her E in order to not only have guarentee slams, but to also gain an advantage.
She needs to be near her tentacles or else when she W's they wont even move.
She needs her R active in order for her tentacles to actually hit the enemy. The only time her tentacles normally hit the enemy is when she is in laning phase with her Q or the enemy doesnt know how to dodge her tentacles in lane which is most of her damage.
If she has no tentacles near her then she needs to land E+R to have a chance. If she misses her E then she will just spawn 1 tentacle vs 1 person and the enemy will almost not lose vs her then because her damage is pitiful.
Illaoi needs to burst and kill her enemies within her 8 seconds of ult active. If she doesnt then she will probably die or nothing comes from it.
Compare her to literally any other juggernaut(except Yorick) and watch how none of them are reliant on one specific combo to have a chance to fight their opponent.
just needs to build stacks and position himself so that his Q hits the enemy with the blade. He isnt reliant on any specific combo to acheive this.
is probably getting a relaunch but I'll include his current version. All he does is land his cleavers, use his E for damage, and his ult to stay in the fight longer.
besides his villian mechanic giving him more damage, he literally just has to spin on the enemy for damage with his autos being filler.
he just needs to Q, Q, and Q some more to kill the enemy. His ultimate makes his Q have a far lower cd for more damage. The condition Nasus has is having a decent amount of stacks on his Q.
needs to land axes and actually be able to auto attack the enemy champion. His ultimate is there to make him harder to kite and CC. Does not require set up prior besides having his cds up.
is getting a vgu but I'll include him anyways. Sort of needs an ally so that he can get the full use of his W. If not then he just can damage the enemy with his other spells while hopefully staying in range of the enemy.
no real condition to fight an enemy champion besides having her ult ready to use. If she doesnt have ult then she just needs to land E and run the enemy down. Her ult is a bonus and is not mandatory to win a fight.
same as Shyvana, just needs to stay in range and run the enemy down, no need for prep prior.
same as Shyv and Udyr except this guys ult is actually useful. His only condition to win a fight is having his ult up. Does not rely on a combo to win besides landing R and running them down.
this guy has no conditions besides having his W ready to use. He just needs to press W and move around the enemy. His ult is there to make sure the enemy cant escape with low health. His Q and E are there to help him move around the enemy. Does not rely on prep prior. He can fight anywhere at anytime unless he has no shotgun leg charges.
same as Udyr and Shyvana except Volibear has needs his ult for the boost in damage. His only real condition for more damage is getting the enemy low for his bite to kill them.
is similar to Illaoi in lane but loses the needing to build up tentacles/ghouls once he has ult. His ult immediately gives him ghouls without needing to build them up on minions. He needs to stay in melee range of the enemy to deal damage afterwards which he has his E and W to help with. If he doesnt have ult then similar to Illaoi, he needs to build up lots of ghouls prior to the fight. He is reliant on his ult but only his ult come later in the game. If he has no ult or ghouls he is useless.
Edit: added Volibear and Yorick.