Drop doublons Pandas en considérant les minuscules

result_df = df.apply(lambda x: x.astype(str).str.lower()).drop_duplicates(subset=['Column1', 'Column2'], keep='first')

print(result_df)
  Column1   Column2 Column3
0   'cat'     'bat'   'xyz'
1   'toy'  'flower'   'abc'
Thankful Turtle