It's called Liablity Leona for a reason, you're not exactly going to be carrying. The main thought process behind this build is to be as annoying as possible. Maxing your W will enable you to survive engages, with your aftershock making you even more unkillable whilst dealing a decent amount of damage.

Items:

[*] Everfrost Chain the Everfrost root with your Shield of Daybreak and Solar Flare to lock down your opponent as your jungler ruins their day.

[*] Anathema's Chains Increasing your opponents tenacity by 20% means less fun for them, more fun for you. And because who would turn down taking reduced damage, cooldown reduction and health?

[*] Abyssal Mask Applying heavy crowd control to your opponent, such as your stuns and Everfrost root, increases the damage they take from all sources by 15% for 5 seconds! Plus additional HP and magic resist helps.

[*] Horizon Focus Your heavy crowd control increases damage from all sources by an additional 10% and marks (reveals) your opponent for a few seconds.

[*] Lich Bane Purely because it's late game, you should have both W and Q maxed and with the AP from Everfrost and horizon focus your Lich bane will do a decent amount of damage on your Q.