In the Old Testament different animals were sacrificed for different reasons. The lamb was the sacrifice for sins. Only thing is, under that law if you sinned again, you had to sacrifice another lamb. John the Baptist in John 1:29 says, “Behold, the Lamb of God, who takes away the sin of the world.” This is, I believe, what is meant. Jesus was the perfect Lamb, for in Old Testament sacrifices each animal had to be perfect for it to count for anything. If someone had a spotted lamb, when a white one was called for, it wouldn’t be acceptable. Jesus was perfect. He had no “spots” on him. No sin, nothing that would have made him less than perfect.
This one sacrifice is all that is needed because Jesus died for all sins, for everyone. He can’t be resacrificed, only once was needed. This sacrifice is holy because He is holy. His blood was shed to cover our sins. Well, take them away. So it is a full sacrifice, and no one is excluded. So, Holy because he is holy, one because of Him we need no other, perfectly acceptable to God because Jesus was God in the flesh. Only God could pay the “ransom” for our sins. There was no way we could do it on our own. I believe all this is Catholic, but if I’m wrong in something, I’m sure I’ll hear about it. Does this help?