A synonym for “dangerous” that is less severe could be “risky”.
“Risky” implies that there is a chance of harm or negative consequences, but not as extreme as “dangerous”. For example, “Investing in that stock is a bit risky, but not necessarily dangerous.” It suggests that there is an element of uncertainty and potential for trouble, but not an immediate threat of serious harm.
Another option could be “hazardous to a lesser degree”. This phrase clearly indicates that there is some level of hazard, but it is not as intense as being truly dangerous. For instance, “Driving on that road in bad weather is hazardous to a lesser degree than on a mountain pass during a blizzard.” It shows that while there is a risk, it is not as severe as in more extreme situations.
“perilous in a milder way” could also work. “Perilous” usually means full of danger, but adding “in a milder way” tempers the intensity. For example, “Walking through that park at night can be perilous in a milder way if there are some areas that are not well lit.” This description suggests that there is some potential for danger, but it is not as extreme as being in a truly perilous situation.