In order to show constrast, the best transition word would be: on the other hand. Comparatively could also apply sometimes, but it's more used to make comparisons.
The expression "on the other hand" is the most qualified to be used when the writer wishes to establish a contrast between two elements in the same sentence or in the same paragraph, or text.
As for example in the sentences:
"I like you, on the other hand, I don't agree with your opinions."
"Meiosis divides the cell into four cells with half the chromosomes. On the other hand, mitosis divides the cell into two equal cells."
