That alone wouldn’t be enough to cause half of Marineford to be destroyed if Shiki was fighting two people as strong as him.
The fact that half of Marineford still got destroyed and Sengoku who claimed Shiki was his personal business asked for help from Garp shows Shiki > Either of them
The fact that half of Marineford still got destroyed and Sengoku who claimed Shiki was his personal business asked for help from Garp shows Shiki > Either of them