I think Welles finest performance is in 'Chimes at Midnight.'... Probably his most personal, also.

'The Third Man' is good and Welles is good in it, but it's less about 'acting' and more about projecting a certain species of villiany... For a deeper exploration of the consequences of such viiliany I suggest 'The Stranger' with Edgar G Robinson. The entire plot is spelled out in the first twenty minutes, but the acting is so engrossing and compelling you can't look away...