I think that "Великдень" is more Ukrainian way to translate "Easter" then "Пасха".
I fully agree. Marked it to be a primary translation instead of "Пасха", hopefully will work.
The definitions for велике were big and large, but it told me I was wrong for using large instead of big.
That's because "large holiday" is not correct English. "Big" can mean literal size but also has a figurative meaning (e.g. "a big TV star" does not mean literally a large person), while "large" only has a literal meaning.