Lag and fast bowlers
I just played a guy online who bowled at the stumps every time with fast bowlers, never varying his pace. He (or I?) lagged pretty bad so the ball would hang in the bowler's hand before being delivered, which made it pretty much impossible to time the shot since you have to hit the button pretty much right after the ball leaves the hand against fast bowlers. However he didn't lag every time, so if you tried to time the lag which you thought was coming, you would get bowled by the ball that would be delivered immediately from the hand with no lag.
I ended up getting bowled out for like 10 or something which was pretty sick. However, probably 2/3 of the wickets I lose online are to this exact same phenomenon to the point that I just try and play out the overs against fast bowlers if the person in question lags. Of course picking all fast bowlers means you can't do this. Basically it ruins the game - it is humanly impossible to react fast enough to time the ball against this.
Note that slower balls also own people in a similar way but the difference in timing is not as big, so I recognize them as a legitimate part of the game. Also, against anything but fast bowlers you can just wait for the ball to leave the hand, but it is impossible here.