あまりに良すぎて
あまり means not very much
すぎ means too much
When you put them together, which meaning am I suppose to take?
Think of あまり(に) / あんまり(に) as "excessively".
As an adverb, as in this case, it has two possible meanings.
1.
excessively
ワラカワちゃんが作ったケーキ、あんまりおいしかったからお店で買ってきたのかと思った!
The cake Warakawa-chan had made, it was sooo delish I thought it was store-bought!
2.
not very much
ワラカワちゃんが作ったこのケーキ....あまりおいしくない...ね。
This cake that Warakawa-chan has made..... isn't very good, is it?
When used as "excessively", as in the first example as well as in the one you gave, it is followed by the consequences of it being excessively so and so. So, あまりに良過ぎて should be followed by something like 信じられない、びっくりした、etc.
In the following examples, A and B belong to the category 1 while C belongs to the category 2. Also, when used as "not very much", it usually does not take に.
A.「新しいトランスフォーマーの映画見た? あまりに良過ぎて、もう一回見たくなっちゃった。」
Have you guys seen the new Transformer movie!? It was SOOOO good I want to watch it again!
B.「見たよ。 あんまりひどかったから、途中で映画館出ちゃった。」
Seen it. It was so bad I walked out.
C.「私も見たけど、あまり面白くなかった。」
I've seen it, too. I didn't think it was very interesting.
OK, that is my take on it. Now, let's wait for someone who really knows the grammar.... lol