the best Forex broker always ensure best trading environment for using any kind of trading strategies by providing comfortable trading spreads.
I use an FP Markets Raw ECN account to scalp, and FP Markets offers better spreads and commission fees than other ECN brokers. There are no spreading difficulties, and since it is ASIC-regulated, manipulation is impossible.
Each & every broker has something good to offer if you ask me. You just need to find the one that meets your criteria for the best one. As a scalper I wanted a broker with tight spreads, low commission & minimal slippage. Tried demo accounts of different brokers and finally went live with aaafx & tickmill as they are quite perfect match for me.