Here are some words to use instead of "overall," depending on the context:

General:

* In general

* Generally speaking

* On the whole

* As a whole

* In summary

* Taken together

* All things considered

* In the final analysis

Positive:

* Positively

* Favorably

* Successfully

* Effectively

* Satisfactorily

* Well

* Strong

Negative:

* Unsuccessfully

* Ineffectively

* Poorly

* Weak

* Unfavorably

* Negatively

Specific to a topic:

* In terms of [topic]

* Regarding [topic]

* With respect to [topic]

For a summary:

* In conclusion

* To sum up

* To wrap up

More informal:

* All in all

* Bottom line

* The big picture

The best word to use will depend on the specific context and the tone you want to convey.