Small avalanche - trick play
is natural to prevent the ladder, but after , it seems that White has a problem. The tesuji at saves the day.
With the moves up to , Black can cut off , but White takes the corner and manages to escape with as well.
With , White has fallen for the trick play. With the moves up to , Black seals white into the corner while cutting off . White can push through at a, but b is atari, forcing White to capture, after which Black can finish his wall with a move at c.
Update February 2023: As usual, AI has reevaluated this. The difference between this and the "tesuji" diagram above is small; either can be better depending on the rest of the board. White shouldn't play a, but can tenuki here: black's position looks more intimidating than the previous diagram, but white is a move ahead on the rest of the board.
Note also that is a mistake: this move should be at d instead.
is even worse. After , the white groups are disconnected and heavy.
is not so bad if white plays 5 as descent rather than atari.
Update February 2023: KataGo disagrees, and thinks this is worse! See below.
As white descended she has an extra liberty and can push through and capture the stone on the 2nd line in sente, which is a big improvement over the previous diagram. I (Uberdude) think this is playable for white as she gets sente and there is still some aji on the outside: activating the marked cutting stone and the peep at a are things to look forward to.
Update February 2023: is a mistake. Because the marked black stones have an extra liberty, the net starting with at is more effective