I main ragna as well. like each character ragna has a strategy, pressure the opponent. a great anti air that i use is 6A, it leaves you open for some pretty decent combos. you could follow up with an air juggle or 6D JD. Another great ragna strategy is 5C for the first hit. it has such great range you don't have to move from the starting point and its got great frame advantage. from there you can follow up with hells fang or gauntlet hades, which doesn't actually combo but it is an overhead so its pretty hard to block. if you opponent is always blocking you really want to work on your high low mix up. try 5B 2B 5C 2C then combo whatever special move you like. 3C is an excellent sweep and if your fast enough throw in 2 2 C and ragna will grab them off the ground. or you can follow 3C with dead spike or inferno divider. a really great combo i like to use is 2D it will ground them then go with 5C jC into his air juggle. as for the carnage scissors it will only hit once if the first hit is blocked. its a great move but it has almost no invincibility. during the first few seconds but not during the dashing animation. but don't use it alone try using 5D and immediately follow it will carnage scissors. it will combo and it take a pretty good amount of damage. remember combos are sweet and all but if you really want to turn the tide don't use a stupid long combo, the more hits you get in the less damage your combo will do. and delayable means you can do the motion for hells fang and immedietly follow it with the next hit or wait a few seconds.
i hope this helps. i know ragna's combos inside and out so lemme know if you need more help!