Question: What wicked thing did Pūtanā do that made her a demon in this life? What good thing did she do that led to her being killed by Kṛṣṇa Personally and getting liberated?
Answer by Romapada Swami:
The good thing Pūtanā did was that she was the sister of Bali Mahārāja in her previous life.
When the sister of Bali Mahārāja saw Lord Vāmana, she was astonished at His beauty. She had a desire in her heart that – if possible – she would like to have this boy as her child with maternal affection, feeding Him, holding Him, and coddling Him.
The Supreme Lord in His form as Vāmana understood her desire.
At that time, silently, He directly gave her this benediction. “So be it!”
The bad thing Pūtanā did in her previous life as Bali Mahārāja’s sister was when she saw that her brother was tied up with rope by Lord Vāmana because he did not give the third step of land to Lord Vāmana, she became very angry.
She desired to personally kill Him.
So in her next life, she took birth as Pūtanā.
Pūtanā’s good fortune was that she got direct contact with the form of the Personality of Godhead Kṛṣṇa.
Kṛṣṇa overlooked the bad thing – her trying to kill Him — and liberated her by killing her.
So her punishment of being killed by Kṛṣṇa was a most amazing benediction: she became situated in the spiritual world as an assistant of Mother Yaśodā!