A really fast thesaurus... with lots of synonyms.
Transition words connect ideas: use additionally to add a point, however to contrast, therefore to show a result, for example to illustrate, and finally to conclude.
Transition words are words and phrases that link one idea to the next — showing whether you are adding a point, contrasting, giving a reason, or wrapping up — so writing flows instead of jumping.
Finally, ultimately, and overall all signal a conclusion cleanly; avoid the overused "in conclusion" where a single word will do.