|History's greatest monster.|
Now, I don't mean to boast, but the fact is that I am uniquely qualified to discuss this question, because I have actually killed Baby Hitler. Admittedly, I used my mad alternate-history skillz rather than a time machine, and I didn't murder Baby Hitler so much as I posited an accidental death for him, but a dead Baby Hitler is a dead Baby Hitler, and I'm prepared to put my claim to expertise up against anyone else's.
The dead Baby Hitler question is complicated by the temporal nature of the problem. Time, as others have noted, is not so much a linear progression of cause to effect as a big ball of wibbly-wobbly, timey-wimey stuff. The human consciousness exists in the present, and it remains in the present whether the human involved lives in the year 2015 or travels back to 1889. For the time traveler, being in 1889 cancels out all subsequent events. To the person-in-1889, there is no Nazi Germany, no World War II, and no Holocaust. There's just 1889. And this baby lying in his cradle hasn't done anything wrong; he's just a newborn baby.
On the other hand, the person-in-1889 has, simply by appearing in 1889, created a new reality. Every die that rolled and coin that flipped in the history that led up to our 2015 now has to be re-rolled and re-flipped, with the outcomes yet to be determined. Thus, our time traveler has eliminated the existence of everyone who will be born in the 20th century, an act of mass-murder that makes the Holocaust pale in comparison.
So, it's basically a trick question. The only way to kill Baby Hitler is to snuff out the existence of billions of people,* which pretty much negates any possible positive results from removing Adolf Hitler from history.
Bottom line: Hitler only killed Anne Frank. Jeb Bush would eliminate her from history altogether.
*Unless you do it the way I did it, via a thought experiment.