Too, As Well, and Also are usually used in positive sentences. The only difference is in their placement in the sentence. Too and as well are used at the end of a sentence. (As well is more formal than too). Also usually goes before the verb or adjective.
She likes movies.
- I like movies too
- I also like movies
- I like movies as well.
To express an agreement in negative sentences, Either is used. Either usually comes at the end of a sentence.
She doesn't like soccers, I don't like soccers either.
However, it is possible to have a positive sentence and agree with a negative sentence and vice versa.
1. Joni is doing bad at science class (positive sentence), he doesn't really like the teacher either. (negative sentence)
2. The new DC movie isn't that good (negative sentence), and I also prefer Marvel's. (Positive Sentence)