I saw this video on the internet of this summoner and so I could analyze it uses Light Set retributer amarantine (do not know the Enchantments) like a hero or an experienced person at level 99 summoner who plays the same way you can tell which weapon she uses dyes which which in September which weapon to use and how much M.atack. you need to cause such damage to the marks.
You don't need much actually.
As you can see arround the 4:50 in your vid, she deals 32k to her target.
As a summoner you have 2 good nukes, Invoke and Mark Retriever.
If you have a decent retributer (2sa/300) and 2 M.Crit Damage rings you can easily crit arround 20k with Invoke, as for Mark Retriever, it's better used when your target has the 3 marks on him (Mark of weakness, plague and trick) and you will also crit for big numbers.