This is the 4972nd most frequent Russian word.
красивую
"Beautiful" (feminine, accusative case).
Describes the quality (beautiful) of 'картину' (the painting), which is a feminine noun in the accusative case.
Я вижу красивую картину.
I see a beautiful painting.
Describes the appearance (beautiful) of 'девушку' (the girl), a feminine noun in the accusative case.
Мы выбрали красивую девушку для роли.
We chose a beautiful girl for the role.
Describes the quality (beautiful) of 'вазу' (the vase), which is feminine in the accusative case.