It seems a bit weird to have a post devoted to combat, when, unlike most games, Krendel does not have a chapter devoted to it.
The first thing to understand about combat in Krendel is that it works just like everything else. The tests are the same, powers work the same, environment works the same, and so forth. In fact, the combat section only addresses a couple of special rules, like acting into a crowd, surprise, bouncing grenades, and the like.
It would be fair to say that combat does emphasize certain universal rules, like measurements, that other encounters don't. Initiative and tracking time by rounds isn't that necessary in other types of encounters. Distance, concealment, and cover, where important for seeing and avoiding things, can also play a big role in combat. One unit of measurement of particular note is the space. It is a square or hex that measures one meter at its shortest dimension. This lets you use a square grid or a hex map if you want to plot your combat out with minis. You don't have to, but the option is totally there.
Even with all that stuff above, combat in Krendel feels different. As mentioned in the post on the core mechanic, you can tailor your action via successes. So you can choose to deliver a heavy blow, or you can deliver a lighter blow and take another action. Of course, different actions can provide different options.
Another difference is that the average character is mortal. Humans get 8 Health. A competent character has a level 2 in a skill, for a target number of 6. A broad sword or a hunting rifle will have a weapon factor of 2. So if you rolled a 6 (your target number) and spent all 6 successes on damage, then you'd deal 8 points of damage. Yep, you just one shotted your opponent, feel free to describe how awesome that action was.
Also, size matters. More accurately, Scale matters. Boy, does it matter. Scale is an approximation of the dimensions of the principle actors. In a human-centric game (even with elves and whatnots), Scale 1 = 1.4 to 2 meters. All damage (and Health, distances, etc.) from successes are multiplied by that Scale. So, the Scale 10 igneous scourge (some 20 meters big) will deal 10 damage per success. It sneezes, you die. Yes, that can be a bit of math, but it is also pretty realistic. It doesn't matter if you are in plate armor, if you get clipped by a truck, its going to leave a mark.
A few items change things up. First is equipment. Weapons add their weapon factor to the damage dealt. Armor subtracts its armor factor from the damage dealt. Item qualities can let you (or prevent) bypass armor or set a foe on fire or give you a bonus when you charge, or any number of other things. Artifacts, be they magical or technological in origin, are very much like those you find in Diablo: you just start attaching item qualities as prefixes and suffixes to build what you want. It makes for a lot of options.
As potent as equipment is, powers are equally (and arguably more) important. Most games offer warriors the ability to attack more or be a better meat shield. I grew bored with these archetypes quickly because they offered so few options for interesting play. Even in combat, where the warrior is supposed to shine, I grew bored. Rogues and mages generally got me going since they offered options and their limitations made me consider other approaches. So, when designing Krendel, warriors got special attention.
The first key to playing a fighter is finding the right stance for you. Stances are powers that you can activate as a free action. Once activated, they provide a passive benefit for as long as they remain active. With a couple of exceptions you cannot have more than one stance active at a time, but you are welcome to switch them around. Stances are essentially fighting styles with fancy names. There's pearl tear for the dodge based light fighter, opal wind for the two weapon fighter, citrine perch for the sniper, and a few more. There's even a stance or two for characters that focus on non-core powers, like sorcerers or psychics, not to mention the focus method is based around its own, specialized, group of stances.
The next key to playing a fighter is choosing the right boosts for your weapons. Boosts augment another action. Powers that are boosts typically cost one power pool. For example, jarring blow boosts any attack so that if the attack succeeds, the target also gains the staggered condition. It is important to note that you can use a limited number of boosts simultaneously, based on your skill level. Many core boosts inflict conditions, but they are generally limited only to weapons covered by one of your expertises and/or to weapons that inflict particular damage forms (e.g. bludgeoning damage), which is also one of the few times you will care about the type of damage your weapon deals.
I should probably make a quick side bar about damage forms. These are the types of damage an attack does. Most of the time the damage form does not matter. If untrained me swings at someone with a knife, club, spear, or torch, it will not matter if I am dealing slashing, bludgeoning, piercing, or fire damage. They come into play if a target is resistant, immune, or vulnerable to a particular damage form or if you are performing an action that keys off one. For example, flensing strike, can only be activated when using a weapon that deals slashing or piercing damage. So, you couldn't use it with a club.
Back on track, like all characters, a fighter archetype can also benefit from developments: powers that confer constant, passive effects. These can include making armor easier to wear, giving you an extra counter (seriously, you will want alertness so much in combat oriented games that there's even an optional rule for just granting it to player characters), reducing the effects of concealment, and giving you extra Health.
Non-core characters don't lack for combat ability, but they don't have to focus there. Each power method, even core, provides many options that can be used outside of combat. Importantly, most powers require the expenditure of one power pool or one power well. The former regenerates after each encounter, where the well only refills at the end of the day. This means you can easily run out of fuel for your powers if you are not careful, but you can also get ready again without too much effort.
If you want to see some example archetypes with explanations of what they can do and how they can develop, check out Appendix E in Krendel Core.