The Hardest Skill Cape?

I'd disagree that Herblore is the hardest, simply because people who can afford it can just 'buy it'. It would take time to get 99, but it's still 'buyable'.

I'd say any skill that isn't buyable have to be hard, such as Summoning, Slayer, Agility etc.

In fact, not only is Summoning simply an 'un-buyable' skill, but it also costs a bomb for the Shards in large quantities (even if you swap Pouches for Shards, you only get a certain %).

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In my opinion though, the hardest skill to get 99 in is Agility.

It is a constant bombardment of clicking, you have to constantly watch the screen in time for the next click. In some skills you have things in your inventory where you can just click 2 or 3 times then watch as the system does the work for you, then you just have to bank and repeat.

If we went back to old RuneScape where there was no 'make x', then maybe I would say different than Agility but we're not playing the old version =)