Did it reflect poorly on St. Francis De Sales that he offered a bribe to convert Beza? St. Francis De Sales offered a 4,000 dollar pension to Theodore Beza. Source. It is very difficult to see this as anything other than "Oh boy, none of my arguments are working. Here! I'll make one last-ditch effort by appealing to greed!" Isn't this kind of embarrassing for Catholics that they canonized a man who thought that you could buy someone to conversion?
Theodore de Beza was a close friend of, and collaborator with, Calvin. When Calvin died, in 1564, he became his successor as the spiritual leader of  the Republic of Geneva. Although Beza was not quite ten years junior to Calvin, he survived him by over forty years.

He was a scholar and a very influential Protestant who had travelled widely in France and Germany as well as Switzerland. By the late 1590s he had relinquished most of his public duties and was in his late seventies (he was born at Midsummer in 1519). 

St. Francis de Sales was, in April 1597, not quite thirty. He had already had some success in converting Protestants to Catholicism and had received permission from the Pope to read Calvin's Institutes and other works.

The Protestant cause in Europe  had been weakened by the conversion to Catholicism of Henry IV of France, in 1593. He was said to have remarked  "Paris is worth a mass."  

St. Francis de Sales and his friend Esprit de Beaume conceived a plan to convert Beza to Catholicism. Beaume was to obtain from the Pope assurances that Beza would be welcomed if he converted to Catholicism.  Sales was to use his skill and zeal to persuade Beza that his Protestantism was in error.

The renunciation of Protestantism by such an influential figure as Beza might be expected to cause a collapse in confidence in Protestantism, and not only in France. Sales and Beaume did not seek to convert Beza solely out of a concern for Beza himself, but for the weakening of the Protestant cause generally, and so indirectly for the conversion of many. 

De Sales met with Beza in Beza's  home, which had been Calvin's home, in Easter Week 1597, and again later that month. Both had been born into minor nobility. Both were keen and zealous exponents of their respective beliefs. Beza was 77 and Sales 29. Neither man converted the other. Sales was initially hopeful in that Beza conceded some of his points, but that did not mean Beza accepted Sales conclusions. Neither man converted the other.  

In July, realising that Beza was not about to change his beliefs, De Sales offered him, on behalf of the Pope, a lump sum and a pension for life, if he would at least abandon Geneva. Beza refused to hear any more.
Beza had been in receipt of a pension from Henry IV which ceased on the latter's conversion, and still had his pastor's salary.

De Sales would have liked to  convert Beza, but failing that bribing him to abandon Geneva, or to renounce Protestantism insincerely (the terms which might have been agreed cannot be known since Beza drew the discussion to a close) would also weaken Protestantism and so was a good thing, from a Catholic perspective.

Having failed to convert Beza, or to induce him to leave his post, the next best thing was to convince people that he had done so, or was about to do so. Rumours were circulated that Beza and the Republic of Geneva were returning to Rome. The people of Sienna, in Italy, were convinced Beza would pass through Sienna on his way to Rome and gathered to welcome him at the time he was due. 

Rumours then began that Beza had died on the way to Rome, or had converted on his deathbed in Geneva.  Beza himself assured people he was alive and Protestant. 

De Sales did not believe that he could buy Beza's conversion, but did hope to buy his influence.

Whether this reflects poorly on him is ultimately a matter of opinion, and will depend on how important one feels it was to weaken Protestantism, and in so doing bring many to the Catholic Faith. 

This article describes the matter from Catholic sources. See also this.