Being competitive helps the competitor in the process of you competing, for example, in a price competition, you may keep decreasing your price to beat your competitor, and that competitor will decrease their price to beat your price. In the process of that, you guys will gain more customers and revenue, unless your price gets too low and you start making less marginal rev than marginal cost, and the business is forced to shut down. If a business is overly aggressive, they might collude with the other businesses to beat yours and they might start using ad-hominem, i.e saying that "Our prices are lower than that of your business!". Thus being overly aggressive just leaves the other competition offended.
What is the difference between being competitive and being overly aggressive?