Mix cranberries and sugar together in a bowl. Cover and refrigerate, 8 hours to overnight.

The next day, beat cream in a chilled glass or metal bowl with an electric mixer until soft peaks form.

Remove cranberries from the refrigerator. Mix in drained pineapple, marshmallows, pecans, and whipped cream until well combined. Pour into a 3-quart dish, cover, and refrigerate or freeze for at least 1 hour before serving.