The evidence for evolution is very strong, in fact there are more evidences for the theory of evolution than any other scientific theory. The main drive to create the illusion that there is a "controversy" between the theory of evolution and "creationism" is to give the false impression that the two positions are on equal levels and have the same evidential merits. This is simply not the case and never was the case. The scientific evidence only sided one position: evolution.
So in order to counter the facts, creationists have created several illusions that the facts are wrong or do not exist at all (like saying not a single transitional fossil exists). Creationists think if by somehow disproving the theory of evolution somehow means creationism wins by default or lends it credibility. Creationists also try fear mongering and paranoia, telling many dedicated belivers that holding their religious beliefs while accepting the fact of evolution is abominable and damnable or can lead to atheism, nazism, communism, or anything scary they can think of. Other creationists tactics include deliberate deception by creating frauds (fake dinosaur footprints, fake images of animals that resemble dinosaurs carved on artifacts or stones, and much more). Creationists also try to recruit scientists to argue in favor of creationism, or they have some stern believers obtain fake scientific credentials to masquarade as legitamet scientists. Once this has been achieved, they use faulty psuedoscience to argue against evolution and they do not submit their work to credible academia. Their arguments are not scientific, and they will frequently straight up lie to their audience (such as saying the Flood was created by an Ice Shield around the Earth; Adam lived for 900 years; dinosaurs could breathe fire; the Grand Canyon was formed by the Flood; the list goes on and on).
When all this fails, creationists try to use their political powers by trying to convince legislature to mandate that schools teach creationism as an "alternative" science course/lesson. The main problem is that they are pushing a view that is clearly not science, and in so doing they are pushing a certain religious beliefs (which breaches the U.S. Establishment Clause). To this day, creationists use this method because it is their only option. Some try to rephrase the wordings in creationism, such as calling it "intelligent design" (ID), or try to rewrite science altogether. Others try to put the schools on a voucher program, and thus insert creationism into the ciricullum. One of the key significant points to note here: they are not using science to present creationism as science.
Despite creationists denial of the evidence, the evidence speaks for itself: evolution is a fact.
This is a key point creationists try to attack. Creationists often misinterpret the fossil record and imagine there are no transitional fossils. This is Complete Bogus!
Even before Charles Darwin went public, we already had discovered several fossils that were later identified as "transitional." Even though the collection was poor at the time, and Darwin was aware of it, 150 years since then we have found thousands of transitional fossils (much more than Darwin could have reasonable hoped for). And yet creationists are denying that we have even found a single one. They often demand we find a fossil of an animal that was so bizarre and unrecognizable from its parents that we could not tell the difference (like Kirk Cameron's Crocoduck) despite evolution never proposed this and in fact it would disprove evolution.
They often say that whale evolution is so god-damn impossible, the transitional species would die, because it can't "live" on land or in water. Well, they forget Ambulocetus, which is an animal that could walk as well as swim. They ignore Australopithecus afarensis, or thrinaxodon.
Today there are otters that live partly on land and partly in water. This shows animals that spend time in and out of water can survive.
Creationists also point to fossils and say things like "no, it doesn't count because its 100% fully-formed bird (or whatever)." When questioned to pin down why they say these things, they often have to resort to ignoring the mosiac of transitional traits and focus on a certain set to argue that it is only one "kind" of animal.
"Kind" is a favorite creationist term that is always undefined and can mean anything from "species" to "family" or even "genus" whenever the creationist whims it.