Which of the following show maximum bond-order? 

$\because$ Bond order $\left(\mathrm{BO}\right)=\frac{{\mathrm{N}}_{\mathrm{b}}-{\mathrm{N}}_{\mathrm{a}}}{2}$

Here, ${\mathrm{N}}_{\mathrm{b}}$ and ${\mathrm{N}}_{\mathrm{a}}$ are the number of bonding and anti bonding electrons, respectively.

for ${\mathrm{O}}_2,\mathrm{BO}=\frac{10-6}{2}=2$

for ${\mathrm{O}}_2^{-},\mathrm{BO}=\frac{10-7}{2}=1.5$

for ${\mathrm{O}}_2^{+},\mathrm{BO}=\frac{10-5}{2}=2.5$

for ${\mathrm{O}}_2^{2-},\mathrm{BO}=\frac{10-8}{2}=1$

Hence, maximum value for $\mathrm{BO}$ is for ${\mathrm{O}}_2^{+}$.