It is clear that adjectives of one syllable normally end in -er and -est in their comparative and superlative forms whilst the comparative and superlative of adjectives with three or more syllables are formed with more and most:

• The water in the pool was colder than I expected it to be on what was the hottest day of the year.
  
• They always go to the most expensive restaurants where you can see the most glamorous people in the world.
  
• The work I do is now more satisfying because the conditions under which I work are more satisfactory.
  
  

-er /-est or more/most with two-syllable adjectives?

When it comes to two-syllable adjectives, the case is less clear cut. With some two-syllable adjectives, -er/-est and more/most are both possible:

• The water here is shallower / more shallow than it is further up the beach.
  
• The grey squirrel is one of the most common / commonest rodents that you will see in England.

Others, with particular endings, tend to folllow either one or the other pattern:

-y > -ier

Two-syllable adjectives which end with consonant + -y nearly always form their comparatives and superlatives with -ier and -iest:

• You are one of the messiest people I know. Even Jane is tidier than you are.
  
• I'm busier than I used to be so I have to get up even earlier than before.

It would be unusual, I think, for the comparative or superlative to be formed with more or most in these examples. However, in your example, Kim, with risky, both patterns appear possible. It may be the case that more risky works well here because it is combined with a modifying phrase such as a lot. Compare also the following:

• Walking along this mountain path is much more risky in winter than it is in summer.

However, as a general rule, stick to -ier / -iest with two-syllable adjectives which end with consoant + y

-ful / -less / -ing / -ed / -ous

Note that two-syllable adjectives with these endings always form their comparatives and superlatives with more and most:

• Having a tooth extracted was more painful than I expected it to be.
  
• The situation is even more hopeless than I thought. She will never recover.
  
• The most boring part of the weekend was listening to Jane's jokes.
  
• I'm more worried than you are about Tom and I've only known him for two days.
  
• The two brothers are both well-known internationally, but I would say that Giles is the more famous.

Note that when we are making the not-so-much comparison, less and least are the only options open to us, unless we use the construction not as…as:

• I'm not as hungry today as I was yesterday.
  
• I am less hungry today than I was yesterday.
  
  
• I was angriest with John about the spoilt weekend. I'm less angry with you. But I'm still angry, nevertheless.
  
  
• Why don't you sit here? This is the least uncomfortable of our chairs.
  
  Note that we tend not to use less and least to form comparatives / superlatives with one syllable adjectives, as short adjectives often have other words as their opposites. Compare the following:
  
  
• Your cooking is less bland than Mary's. - Your cooking is spicier than Mary's.
  
• It's less warm today, don't you think? - It's cooler today, don't you think?