This is for completing all of Donovan's challenges in Night Warriors. To avoid confusion whenever I say forward I mean the kick not the direction. If I am referring to the direction I will say toward. Also if you need any of the terminology below explained to you or you are still stuck on a combo after reading the guide, simply leave a comment and I check TA daily so you shouldn't have to wait too long for an answer.
Simply stand next to the opponent and input a HCB followed by a punch.
If you stand next to the opponent before doing the dash and you cancel it fairly quickly with the the forward, you can just input a QCF followed by a jab to cancel the forward into Ifrit Sword. So input toward toward forward QCF jab. Or if you're not quick enough you can just hold toward the second time you press it for the dash, then press forward, release toward and do the QCF jab.
You just need to be quick for this one and unfortunately you can't hold toward during the shorts. So do short, short, short, timing is quick and in rhythm, then when the animation for the third short starts immediately input the DP followed by a punch.
Stand a few paces away from the edge of the screen, input a HCF followed by the 3 punch button (LB by default), Then when Donovan finishes his animation input a HCF followed by roundhouse.
This combo is all about distance and timing, use the fierce+roundhouse version of Killshred Plant, plant it in the center of the screen. Position the opponent a few paces away from the sword, then jump over the opponent so that you're standing next to them. When you are in the correct position press strong immediately followed by fierce+roundhouse, you have to be precise or you'll end up doing a chain combo. Now the idea is that the sword hits the opponent as it leaves and when it does you immediately start the next part. For the next part it wants you to do 3 standing shorts followed by toward roundhouse. Now short to toward roundhouse happens very quickly but the pace you press the shorts at can vary and still connect. The way the game wants you to do it is to do your standing shorts at a slower pace than what is possible so you can synch up with the sword upon its return. However all of this timing can be negated by doing 4 standing shorts as quickly as possible instead of 3 timed shorts. Immediately follow the fourth short with a toward roundhouse. I assure you it is much easier to do 4 shorts pressing the button rapidly than it is to learn the very specific timing of 3. Once the toward roundhouse connects the sword should hit the opponent straight after if you did everything right, once the sword hits do 4 very quick jabs followed immediately by a strong, the first jab should be with your fist as the sword has yet to return to you, the next 3 will be with the sword as will the strong. So just make sure you can do 4 jabs followed by a strong on its own and have it say 5 hit chain before you attempt the combo. If you follow what I said about doing 4 rapid shorts instead of 3 timed ones it should make this combo much easier.