Demon's Souls. Spending 45 minutes to get to a Demon only to have him roflstomp you as soon as you walk in, depleting you of all those souls, and 45 minutes of your life. Then when you get almost right back to his chamber, a katana skeleton spams his jump/slash attack twice in a row, first killing your shield then killing you, effectively setting you back 90 minutes with nothing - not even souls - to show for it.
Angry.
Angry.