Reaction of ethylene glycol with acidified potassium permangnate
I think the final oxidation product should be carbon dioxide ($\ce{CO_2)}$ if acidified potassium permanganate is present in excess amount.

Firstly, ethylene glycol will be oxidised to oxalic acid. But oxalic acid can still be oxidised. In fact, it is the concept of titration of oxalates with potassium permanganate ($\ce{KMnO_4}$). Under acidic conditions, oxalic acid ($\ce{H_2C_2O_4}$) will be oxidised to $\ce{CO_2}$ by $\ce{KMnO_4}$ as:

$$\ce{2MnO_4^- + 5C_2O_4^{2-} + 16H^+-&gt; 2Mn^2+ + 10CO_2(aq)  + 8H_2O}$$ 

Thus the final product should be $\ce{CO_2}$

Also, note that, formic acid is an oxidisable acid because it gives silver mirror in reaction with Tollen's reagent $(\ce{[Ag(NH_3)_2]OH})$, and thus, formic acid can not be the end product, as it is still oxidisable and hence it will definitely react with acidfied $\ce{KMnO_4}$ if both are present in  the reaction medium.