What you are looking for is acetylen's combustion reaction, which can also be viewed as an oxidation-reduction reaction.
#2C_2H_2 + 5O_2 -> 4CO_2 + 2H_2O#
Let's assign oxidation numbers for all atoms involved in the reaction
#2C_2^(-1)H_2^(+1) + 5O_2^(0) -> 4C^(+4)O_2^(-2) + 2H_2^(+1)O^(-2)#
We can see that #C#'s oxidation number goes from (-1) on the reactants' side, to (+4) on the products' side
#C^(-1) -> C^(+4) + 5e^_# (for each individual #C# atom);
#O#'s oxidation number went from (0) an the reactants' side, to (-2) for both products
#O^0 + 2e^(-) -> O^(-2)# (for each individual #O# atom);
The total number of electrons lost by #C# is #4 * 5e^(-) = 20e^-#, while the total number of electrons gained by #O# is #8 * 2 e^(-) + 2 * 2e^(-) = 20e^(-)# -> determined from the balanced REDOX reaction.
Therefore, #C# is being oxidized - acts as a reducing agent, while #O# is being reduced - acts as an oxidation agent.
