In my opinion Kabal is hard in the sense that he is execution heavy, but Raiden is harder because it overall takes strong fundamentals to do well with him. As far as pressuring with Raiden you have to play good footsies and fill in holes in your offense with 1's, D1's, D3's etc and make good reads. Also F23 by itself is a good pressuring tool because it leaves you at 0 on block and jails so you can land vicinity blast, which leads to a plethora of options after blocked by your opponent. B3 / B31 into throw, D3 into throw, stand 1 on hit into D3 F24 etc.
B312 and 334 are good pressuring tools but interruptible...it's all about switching it up depending on whether or not your opponent is interrupting, also teleport in neutral/slight disadvantage situations such as after a vicinity blast or after the recovery of F23/F24/334/all points in B312 can be good for opening up your opponent/playing mind games. Basically pressuring is about intelligently using Raidens strings in the right situations making good reads/knowing whether you are at advantage or disadvantage.