views - remove duplicates based on field value
I would use Views Distinct module to filter the duplicates out. The way this works is this:


you select the displayed view field,expand 'Views Distinct Settings' and select 'Filter Repeats'


So, for your particular case, if you want to show only the last payment method, order by payment method (ID ?) DESC, and on the order_id filter repeats. This way, only the last row for every order_id will show.