In the level Temple Of War, starting from the teleport stone, make your way up and to the right as shown from 0:11-1:17. This was my first time through so I apologize for the missed jumps.
I did not realize I was going to fight so many enemies, which is why I turned the intenso off at 2:02. Then, when I realized how many enemies were coming, I reactivated it at 2:05 and unlocked both achievements for the 125 hit combo and 20 consecutive kills in one intenso sequence.