aggressive describes a very "active state of attitude" on doing something.
for example: as a green hand in this company, you have to be very aggressive in learning lots of things because you can barely expect someone will patiently give you a hand.
ambition means an "eager or strong desire to achieve something", such as fame or power.
for example: i always encourage young men to build up a big ambition for their future. and bravely go for it.
and of course, we can also use these 2 words in a sentence like this....
"i have to tell you that your ambition won't be realized if you can't ask yourself to take very aggressive execution."