The bond order is directly related to bond strength. Higher the bond order higher will be bond strength.

KO2 is an ionic compound, on separation of ions we get K+  and O2 - ion.

O2-(peroxide ion ) have a bond order of 1.5

In O2[ptF6] when we separate ions we get O2+ and [ptF6]- ions .

The bond order of O2+ ions is 2.5

As O2 + ion has higher bond order then O2-  , so we can say that O2 [ptF6] has higer bond strength then KO2.

Hope you find this answer helpful.