Among group 14 elements, most acidic oxide is formed by

Generally in a group from top to bottom the acidic nature of oxides decreases and basic nature of oxides increases.

Among IV A group oxides, the must acidic oxide is CO₂.

The order of acidity is as follows: ${\mathrm{CO}}_2>{\mathrm{SiO}}_2>{\mathrm{GeO}}_2>{\mathrm{SnO}}_2>{\mathrm{PbO}}_2$