The oxidation state of central atom, 'Xe increases from +2 to +4 to +6 in XeF2,XeF4 and XeF6 respectively. Thus, its tendency to accept electrons also increases and thus, its oxidising power increases. Also, XeF6 can give more fluorine than XeF4 and XeF2. So, the fluorinating agent order is XeF6>XeF4>XeF2. Hence, the correct decreasing order of the given ' Xe ' compound to act as both fluorinating and oxidising agent is XeF6>XeF4>XeF2.