There is no reference throughout Mercutio's tirade of anyone being more dangerous than Tybalt. He does pity Romeo though, for having to answer Tybalt's challenge:
Alas poor Romeo! ...
and is he a man to encounter Tybalt?
He clearly questions Romeo's ability to fight Tybalt.
In speaking about Tybalt, Mercutio mentions the following:
More than prince of cats, I can tell you. O, he is
the courageous captain of compliments. He fights as
you sing prick-song, keeps time, distance, and
proportion; rests me his minim rest, one, two, and
the third in your bosom: the very butcher of a silk
button, a duellist, a duellist; a gentleman of the
very first house, of the first and second cause:
ah, the immortal passado! the punto reverso! the
Mercutio says that Tybalt is very well-versed in the art of courtesy, of extending to others the best forms of ceremonial greeting and display of friendship. He is clearly impressed by Tybalt's swordsmanship and praises his skill with the blade. Tybalt is almost the perfect duellist, who knows exactly when and where to strike. When he does strike, he does so accurately. He has perfect timing and he is quick, because he would have struck even before you knew it or before you could count to three. Furthermore, he understands the art of quarrelling and can argue both the first and second causes for a fight, as well as any lawyer can. Mercutio is so much in admiration of Tybalt expertise that he uses exclamation about aspects related to Tybalt's art. Each reference relates to a particular movement in duelling, such as the 'passado', the 'punto reverso' and finally, the cry 'hai' when an opponent is struck.
Mercutio then expresses his resentment, spiced with some jealousy or envy, for Tybalt's and his followers' affectations and mannerisms:
The pox of such antic, lisping, affecting
fantasticoes; these new tuners of accents! 'By Jesu,
a very good blade! a very tall man! a very good
whore!' Why, is not this a lamentable thing,
grandsire, that we should be thus afflicted with
these strange flies, these fashion-mongers, these
perdona-mi's, who stand so much on the new form,
that they cannot at ease on the old bench? O, their
bones, their bones!
It is clear from these lines that he believes that Tybalt and his friends put on airs and manipulate the way they speak. It may be a kind of exclusive mannerism in language that they have adopted, which Mercutio clearly does not like. It is clear that Tybalt and his group are fashionable and set new trends and Mercutio clearly dislikes the idea that they are so popular. He would have preferred them sticking to the old styles instead of them being so observant to the new forms (which they, of course, have introduced). His language is quite cynical for he refers to them as 'strange flies' suggesting that they are a nuisance. He does, however, concede that Tybalt is full of spirit and an excellent duellist. He also suggests that Tybalt seemingly plays the field - he is 'a very good whore'.