[ComplexInterest]

     I noticed that in the reversible reaction Fe³⁺(aq) + SCN(aq) ⇌ FeSCN²⁺(aq) the addition of SCN moves the equilibrium more to the right than the addition of Fe³⁺(The addition of 1 mol of SCN will redden the solution more than the addition of 1 mol of Fe³⁺).
     I take this is due to the nature of metal complexes, but I'm not quite sure what exactly is the reason that the addition of a ligand molecule has more effect than the addition of a donor atom. Any help is appreciated.

[AWK]

You answered for your question at the beginning - this is equilibrium (with relatively low constant of formation).

[Borek]

What are the initial concentrations?

Calculate concentration of the complex for each case, this is relatively easy equilibrium problem.